Bornite

Bornite (Cu5FeS4) is a copper iron sulfide mineral commonly found in hydrothermal veins, contact metamorphic rocks and in the enriched zone of sulfide copper deposits. It is a common ore of copper

and is easily recognized because it tarnishes to iridescent shades of blue, purple, green and yellow. It is often mined as an ore of copper.

Bornite stands out for the amazing metallic blue-green color it

turns after exposure to the air. That gives bornite the nickname

peacock ore. The colors are from an iridescent tarnish that

forms on bornite upon exposure to air. The tarnish is made of

assorted copper oxides or hydroxides that form a mere atoms thin

layer over the bornite. The thickness of the layers is close to the

wavelength of light. When light waves bounce between the

bornite surface and the top of the tarnish layer they will leave with

the wavelengths of various colors. This effect is the same as the

rainbow effect that occurs with oil on water. In the case of bornite,

the tarnish will have a purplish, violet or blue color. Because

bornite is often intergrown with chalcopyrite which tarnishes to

more greens and yellows, the peacock ore may have many colors

ranging from purple to blue to green to yellow.

In Cornish mines it was known as 'horse-flesh' ore, because it has

is pink copper color.

FIGURE 2

Bornite's crystals, if found, are usually distorted cubes with curved faces. Even rarer are the distorted octahedrons and dodecahedrons. These are isometric crystals. However, bornite's structure at normal temperatures is not isometric. Bornite is only isometric at temperatures above 228C and it was above this temperature that the crystals formed. As bornite cooled it structurally altered to possibly a tetragonal structure but outwardly it retained the isometric forms.

Bornite occurs mostly massive, as well as in group of tiny crystals and globular.

FIGURE 3

Other properties of bornite are the following:

Cleavage: Indiscernible

Fracture: Conchoidal

Mohs Scale Hardness: 3

Luster: Metallic

Streak: Grayish Black

Specific Gravity: 4.9 5.3

Rock Type: Igneous, Metamorphic

Pyrite

Pyrite (FeS2) is commonly called Fools Gold because of its similarity in color, shape, and habit to Gold. In the old mining days, pyrite was often confused with gold as they occur together, although Gold and Pyrite can very easily be

distinguished by simple observation and testing of characteristics. Fire was pyrites most prominent gift to human society. Sparks are created when pyrite is struck against metal or a hard surface and this was one of the earliest methods

humans discovered to create flame. Pyrites name comes from the Greek phrase, pyrite lithos, which means stone which strikes fire. Although no longer considered a valuable mineral in its own right, pyrite in a rock often signals the

presence of other hydrothermal minerals and metal ores that do have significant value.

FIGURE 1FIGURE 1

There are other shiny brassy yellow minerals, but pyrite is by far

the most common and the most often mistaken for gold. Whether

it is the golden look or something else, pyrite is a favorite among

rock collectors. It is so common in the earth's crust that it is found

in almost every possible environment; hence it has a vast number

of forms and varieties.

Pyrite has been mined for its sulfur content. During WWII, sulfur

was in demand as a strategic chemical and North American

native sulfur mines were drying up. A sulfide deposit near

Ducktown, Tennessee contained commercially valuable deposits

of pyrite and other sulfides and produced the needed sulfur as

well as iron and other metals. The sulfur was used in the

production of sulfuric acid, an important chemical for industrial

purposes. Now most sulfur production comes from H2S gas

recovered from natural gas wells.

FIGURE 2

Pyrite occurs in all different shapes and forms. The smaller

crystal aggregates may give off a beautiful glistening effect

in light, and the larger crystals may be perfectly formed,

including fascinating perfect cube and penetration twins and

other bizarre crystal forms.

It can form very well crystallized specimens, which occur as

cubes, pyritohedrons, and octahedrons. Combinations of

these forms also occur. Crystals are usually striated. Pyrite

crystals frequently form penetration twinning, especially in

the cubic form. Cubes are often elongated. Pyrite also

occurs as massive, radiating, grainy, flaky, mammilary,

encrusting, nodular, fibrous, and as groups of small

crystals.

Bornite's crystals, if found, are usually distorted cubes with curved faces. Even rarer are the distorted octahedrons and dodecahedrons. These are isometric crystals. However,

FIGURE 3

Other properties of pyrite are the following:

Streak: Black with a slightly green tinge

Hardness: 6 6.5

Crystal system: Isometric

Specific gravity: 4.9 5.2

Luster: Metallic

Fracture: Conchoidal

Rock type: Igneous, Sedimentary, And Metamorphic

Other properties of Bornite are the following:

Cleavage: Indiscernible

Limestone

Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It commonly forms in clear, warm, shallow marine waters. It is usually an organic

sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. It can also be a chemical sedimentary rock formed by the precipitation of calcium carbonate from lake or

ocean water. Physically, limestones are quite impervious, hard, compact, fine-grained calcareous rocks of sedimentary nature. It has a hardness of 3-4 based on Mohs Scale; a quite low porosity;

resistant on weather impact; it has a density of 2.5-2.7 Kg/cc; and it has a compressive strength of 60-170 N/mm2

CHALK

A variety of limestone that probably was formed by the

accumulation of shells of Foraminifera and/or by chemical

precipitation of calcium carbonate. Pure chalk is white, but it

may be stained with iron oxide or other impurities. It is a soft

porous rock that crumbles easily. It has greater resistance

to weathering and slumping than the clays with which it is

usually associated, thus forming tall steep cliffs where chalk

ridges meet the sea. Chalk hills, known as chalk downland,

usually form where bands of chalk reach the surface at an

angle, so forming a scarpslope. Because chalk is porous it

can hold a large volume of ground water, providing a

natural reservoir that releases water slowly through dry

seasons.

LITHOGRAPHIC LIMESTONE

A dense limestone with a very fine and very uniform grain size

that occurs in thin beds that separate easily to form a very smooth

surface. In the late 1700's a printing process (lithography) was

developed to reproduce images by drawing them on the stone

with an oil-based ink and then using that stone to press multiple

copies of the image. The generally accepted theory for the origin

of lithographic and sublithographic limestones is that they were

formed in shallow stagnanthypersaline and anoxic lagoons. The

combination of mild hypersalinity and low oxygen content is

believed to have inhibited the formation of microbial mats and

prevented the invasion of bottom dwelling organisms. Microbial

mats and bottom dwelling organisms would have left fossils, and

bottom dwelling organisms would have churned the accumulating

sediment, producing a less homogeneous rock. Stagnancy was

required to avoid churning or sculpting of the sediment by

currents or wave action.

OOLITIC LIMESTONE

Oolitic limestone is a carbonate rock made up mostly of ooliths (or

ooids) which are sand-sized carbonate particles that have

concentric rings of CaCO3. These rings are formed around grains

of sand or shell fragments that were rolled around on the shallow

sea floor, gathering layer after layer of limestone. A limestone

composed mainly of calcium carbonate "oolites", small spheres

formed by the concentric precipitation of calcium carbonate on a

sand grain or shell fragment. Oolites are small rounded particles

or grains, so named because they look like fish eggs. Oolites

commonly are formed by layers of material (usually calcite), that

have been deposited around some tiny particle such as a sand

grain or fossil fragment and are rolled back and forth in quiet

waters. Some of the oolites may be of algal origin. When the

grains formed by the process are more than two millimeters in

diameter (about the size of the head of a pin), they are called

pisolites.

Travertine

Travertine is a natural stone such as Marble, Granite, Onyx, Limestone, Slate etc. The key difference between Travertine and other natural stones lies in the formation of the rock, the hardness of the stone and the appearance. Travertine is formed in hot springs and/or limestone caves. Travertine is not the same as Marble or Limestone which falls in the metamorphic rock category. Key characteristics of Travertine stone are the holes within the stone which are caused by carbon dioxide evasion.

FIGURE 1

Travertine has a light transmission of typically subtransluscent in

all but extremely thin pieces. It has a dull to pearly or even

subvitreous. It has a hardness of 3-4 on Mohs Scale. Travertine

has a variety of colors, such as, colorless, white, pink, yellow and

brown, with a streak of white. It has a density of 2.71 Kg/cc and a

specific gravity of 1.68. Travertine is a terrestrial sedimentary

rock, formed by the precipitation of carbonate minerals from

solution in ground and surface waters, and/or geothermally

heated hot-springs. Similar (but softer and extremely porous)

deposits formed from ambient-temperature water are known

as tufa.

FIGURE 2

Modern travertine is formed from geothermally heated

supersaturated alkaline waters, with raised pCO2 ). On

emergence, waters degas CO2due to the lower atmospheric

pCO2, resulting in an increase in pH. Since carbonate solubility

decreases with increased pH, precipitation is induced.

Precipitation may be enhanced by factors leading to a reduction in

pCO2, for example increased air-water interactions at waterfalls

may be important, as may photosynthesis. Precipitation may also

be enhanced by evaporation in some springs. Both calcite and

aragonite are found in hot spring travertines; aragonite is

preferentially precipitated when temperatures are hot, while

calcite dominates when temperatures are cooler. When pure and

fine, travertine is white, but often it is brown to yellow due to

impurities. Travertine may precipitate out directly onto rock and

other inert materials as in Pamukkale or Yellowstone for example.

FIGURE 3

Travertine is often used as a building material. The Romans

mined deposits of travertine for building temples, aqueducts,

monuments, bath complexes, and amphitheaters such as

the Colosseum, the largest building in the world constructed

mostly of travertine. Travertine is one of several natural stones

that are used for paving patios and garden paths. It is sometimes

known as travertine limestone or travertine marble; these are the

same stone, although travertine is classified properly as a type of

limestone, not marble. The stone is characterised by pitted holes

and troughs in its surface. Although these troughs occur naturally,

they suggest signs of considerable wear and tear over time.

Some installers use a grout to fill the holes, whereas others leave

them open travertine can be purchased "filled" or "unfilled." It

can also be polished to a smooth, shiny finish, and comes in a

variety of colors from grey to coral-red. Travertine is most

commonly available in tile sizes for floor installations.

Pumice

Pumice is a type of volcanic rock formed when lava with extremely high levels of water and gases is violently ejected from a volcano. Once the rock hardens, the result is a very light, buoyant

material.

Figure 1

Pumice is a pyroclastic igneous rock. It is formed by volcanic gases that dissolve in liquid magma during explosive volcanic eruptions. The expansion of these gases causes foaming in the lava. When the frothy lava is expelled from the volcano, the liquid rapidly solidifies around the foam, which creates air pockets as the dissolved gases are suddenly released. It can be created by any type of magma, but rhyolite produces more pumiceous stone than basalt and andesite.

Figure 2

Pumice is a type of glass. It is formed by silica-rich magmas that also create obsidian. Traces of minerals such as feldspar, pyroxene, amphibole and zircon are commonly found in pumice. The color of pumice is determined by the type of lava from which it was formed. White pumice is formed from rhyolite, andesite pumices are generally yellow or brown, and basalt forms a pitch black pumiceous.

Figure 3

Pumice appears sponge like. It is rather abrasive and has a gritty feel that is similar to coarse sand. Pumice is an extremely porous glass, which makes it very light. Pumice is so light that it actually floats and says that blocks of pumice have been spotted floating in the ocean after volcanic eruptions. A block can float as far as 4,000 miles before it becomes waterlogged and begins to sink. Pumice is a common ingredient in soaps and cleansers, but it also has many other uses. It is often used by manufacturers to grind glass used in televisions and its light weight makes it ideal for use in landscaping. Pumice stones are also used to exfoliate, smooth and remove dead skin cells.

Calcite

Calcite is a rock-forming mineral with a chemical formula of CaCO3. It is extremely common and found throughout the world in sedimentary, metamorphic and igneous rocks. Some geologists

consider it to be a "ubiquitous mineral" - one that is found everywhere.

FIGURE 1

Calcite, which gets its name from "chalix" the Greek word for lime, is a most amazing and yet, most common mineral. It is one of the most common minerals on the face of the Earth, comprising about 4% by weight of the Earth's crust and is formed in many different geological environments. Calcite can form rocks of considerable mass and constitutes a significant part of all three major rock classification types. It forms oolitic, fossiliferous and massive limestones in sedimentary environments and even serves as the cements for many sandstones and shales. Limestone becomes marble from the heat and pressure of metamorphic events. Calcite is even a major component in the igneous rock called carbonatite and forms the major portion of many hydrothermal veins. Some of these rock types are composed of better than 99% calcite.

FIGURE 2

Calcite is the principal constituent of limestone and marble. These rocks are extremely common and make up a significant portion of Earth's crust. They serve as one of the largest carbon repositories on our planet. The properties of calcite make it one of the most widely used minerals. It is used as a construction material, abrasive, agricultural soil treatment, construction aggregate, pigment, pharmaceutical and more. It has more uses than almost any other mineral.

FIGURE 3

Calcite is intricately tied to carbon dioxide in another way.

Since many sea organisms such as corals, algae and

diatoms make their shells out of calcite, they pull carbon

dioxide from the sea water to accomplish this in a near

reverse of the reaction above. Environmentally then, calcite

is very important and may have been quite important to the

successful development of our planet in the past. By pulling

carbon dioxide out of the sea water, this biological activity

allows more of the carbon dioxide in the air to dissolve in

the sea water and thus acts as a carbon dioxide filter for the

planet. Environmentalists are now actively engaged in

determining if this activity can be increase by human

intervention to the point of warding off the "green house gas

effect".

Alabaster

Alabaster is a translucent stone, usually white, that is used for sculpture and interior decorations. It consists of the mineral gypsum with a very fine grain, massive habit, and even coloring. "Alabaster"

is also used to refer to a similar type of marble, but a better name for that is onyx marble, or even better just marble.

CALCITE ALABASTER

The "Oriental" alabaster was highly esteemed for

making small perfume bottles or ointment vases

called alabastra, the vessel name has been suggested

as a possible source of the mineral name. Calcite

alabaster is found as either a stalagmitic deposit, from

the floor and walls of limestone caverns, or as a kind

of travertine, similarly deposited in springs of

calcareous water. Its deposition in successive layers

gives rise to the banded appearance.

GYPSUM ALABASTER

Gypsum alabaster was very widely used for

small sculpture for indoor use in the ancient world,.

Fine detail could be obtained in a material with an

attractive finish without iron or steel tools. Alabaster

was used for vessels dedicated for use in the cult of

the deity Bast in the culture of the Ancient Egyptians,

and thousands of gypsum alabaster artifacts dating to

the late 4th millennium BC also have been found

in Tell Brak (present day Nagar), in Syria.

BLACK ALABASTER

Black alabaster is a rare form of the gypsum-based

mineral. This black form is found in only three veins in

the world, one each in Oklahoma, Italy, and China.

Alabaster Caverns State Park, near Freedom,

Oklahoma is home to a natural gypsum cave in which

much of the gypsum is in the form of alabaster. There

are several types of alabaster found at the site,

including pink, white, and the rare black alabaster.

Andesite Porphyry

Andesite-porphyry is a porphyry with andesitic chemism. The term porphyry is used for igneous rock composed of large, conspicuous crystals (phenocrysts) and a fine grained to glassy

groundmass (matrix) in which the phenocrysts are embedded. Since the term porphyry refers only to the texture of the rock and not to its composition, the expression porphyritic rock is often used.

ANDESITE PORPHYRY

Andesite is a fine-grained, extrusive igneous rock

composed mainly of plagioclase with other minerals

such as hornblende, pyroxene and biotite.

Color: Variable (gray, rose)

Grain size: Fine grained to glassy matrix, coarse

grained penocrysts

Texture: Porphyric

Class: Igneous Rocks

HORNBLENDE ANDESITE PORPHYRY

This is how an andesite porphyry looks like when other

mineral is present in the ore.

Hornblende andesite porphyry is an intermediate

volcanic igneous rock. Like most porphyrys, it cooled

at two separate rates, causing two sizes of crystals to

be visible.

The mineral assembly is typically dominated by plagioclase, with pyroxene and/or hornblende. Biotite, quartz, magnetite, and sphene are common accessory minerals. Alkali feldspar may be present in minor amounts.

ANDESITE PORPHYRY CLOSE UP

The composition of andesite is classified as

"intermediate" among igneous rocks, implying that its

silica content is in the range of 52-63 percent. Its

texture ranges from aphanitic to porphyritic.

Occurrences: Andes (South America), North Am. (USA: Arizona, Cascades), Italy (Eolian Islands, Tuscany, Umbria), Kamchatka, Japan. Minerals: Phenocrysts, plagioclase, pyroxene and/or hornblende, biotite (+ magnetite, zircon, apatite, ilmenite, garnet)

Malachite

Malachite is a green, very common secondary copper mineral with a widely variable habit. Malachite is perhaps the oldest known green pigment. Typically it is found as crystalline aggregates or

crusts, often banded in appearance, like agates. It is also frequently found as a pseudo morph after Azurite crystals, which are generally more tabular in shape.

Malachite, a copper carbonate, , is

found in varying shades of green. It is 3.5- 4.0 on the

hardness scale with a specific gravity o f3.25- 4.10. It

has cleavage and the fracture is splintery. Malachite

falls within the monoclinic crystal system. It may be

found thin, translucent crystals, but more often seen as

botryoidal, banded opaque masses. It has very strong

pleochroism (colorless, yellow-green, dark green) and

no fluorescence.

The mineral was given this name due to its

resemblance to the leaves of the Mallow plant.

MALACHITE POLISHED SURFACE

The coloring agent is copper, and the malachite is

formed from copper-containing solution or near copper

ore deposits. This oxidation zone of copper deposits

also creates azurite, limonite, and chalcopyrite, which

are all found in association with malachite.

Except for its vibrant green color, the properties of

malachite are similar to those of azurite and

aggregates of the two minerals occur frequently.

Malachite is more common than azurite and is typically

associated with copper deposits around limestone, the

source of the carbonate.

MALACHITE STALACTITES

Archeological evidence indicates that the mineral has

been mined and smelted at Timna Valley in Israel for

over 3,000 years. Since then, malachite has been

used as both an ornamental stone and as a gemstone.

Malachite was used as a mineral pigment in green

paints from antiquity until about 1800. The pigment is

moderately lightfast, very sensitive to acids and

varying in color.

The most important geographic location are in Zaire,

as well as the Ural Mountains, where massive blocks

were mined and became wall paneling and table tops

for Russian czars.

BOTRYOIDAL MALACHITE

Manganese

Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature that is often in combination with iron, and in many minerals.

Manganese ores may accumulate in metamorphic rocks or as sedimentary deposits, frequently forming nodules on the sea floor. It is widely distributed in the terrestrial crust, making it the 12th most

abundant element there. It is a metal with important industrial alloy uses, which is added to improve the strength, toughness, stiffness, hardness, wear resistance, and hardenability of steels. In glass

making manganese is used as a decolorizing agent for green glasses due to impurities. At the same time, it gives glass an amethyst color and is the coloring agent in natural amethyst.

PYROLUSITE

Named after the Greek pyr, for fire, and louo, meaning to

wash, in reference to Pyrolusites use due to its ability to

pull tints from glass. Pyrolusite has a chemical formula

MnO2 and is a common mineral with many localities and

can be found in highly oxidized manganese-rich

hydrothermal deposits and rocks, in bogs, lakes, and

shallow marine conditions, and can often be found as a

product of altered manganite. It has known Physical

Properties: Cleavage: {110}, perfect. Fracture: Uneven.

Hardness: 66.5, to 2 when massive. Density: 5.06; Optical

Properties: Opaque. Color: Light steel-gray, iron-gray to

iron-black. Streak: Black, bluish

black. Luster: Metallic; Mineral Group: Rutile group.

RHODOCHROSITE

Named for the Greek rhodon, meaning rose and chrosis,

meaning coloring. Rhodochrosite has a chemical formula

MnCO3 and is found in low-temperature to mid-temperature

hydrothermal vein deposits, metamorphic rock, commonly

in carbonatites, in sediments either as an authigenic or

secondary mineral, and occasionally in granite pegmatites.

A gemstone with a deep red color and forms during

oxidation of Mn-bearing ores in a carbonate environment. It

has known Physical Properties: Cleavage: {1011}.

Fracture: Uneven to

conchoidal. Tenacity: Brittle. Hardness: 3.54. Density:

3.70; Optical Properties: Transparent to translucent. Color:

Pink, rose-red, pale rose to colorless in transmitted light.

Streak: White. Luster: Vitreous, pearly in aggregates;

Mineral Group: Calcite group.

MANGANITE

This specimen shows incredible, highly reflective luster to

which Ilfeld, Germany Manganites are famous for. The

columnar, shiny black prismatic crystals of Manganite reach

2cm. Manganite has a chemical formula Mn3+O(OH). It is

formed in low-temperature hydrothermal or hot-spring

manganese deposits replacing other manganese minerals

in sedimentary deposits. It has known Physical Properties:

Cleavage: {010}, perfect; {110} and {001}, good. Fracture:

Uneven. Tenacity: Brittle. Hardness: 4. Density: 4.294.34;

Optical Properties: Opaque, transparent on thin edges.

Color: Dark steel-gray to iron-black. Streak: Reddish brown

to nearly black. Luster: Submetallic.

Andesite

Andesite is an extrusive rock intermediate in composition between rhyolite and basalt. Andesite lava is of moderate viscosity and forms thick lava flows and domes.

The word andesite is derived from the Andes Mountains in South America, where andesite is common. Andesite is the volcanic equivalent of diorite.

DACITE

Dacite is a felsic extrusive rock, intermediate in

composition between andesite and rhyolite. It is often

found associated with andesite, and forms lava flows,

dikes, and, in some cases, massive intrusions in the

centres of old volcanoes. Dacite is

the volcanic equivalent of granodiorite.

ANDESITE

Many rocks with an overall fine-grained texture display

scattered minerals that are more than 1mm across.

This porphyritic texture indicates that the magma sat

and cooled a bit below the earths surface, thus giving

time for the large crystals to grow, before erupting onto

the surface and cooling very quickly.

DIORITE

Diorite is a coarse-grained, intrusive igneous rock that is intermediate in composition between granite and gabbro. Its composition is very similar to the fine-grained extrusive rock known as andesite. Diorite is composed primarily of plagioclase feldspar, amphibole, and pyroxine minerals with small amounts of biotite mica. It typically contains very little quartz. When identifying diorite look for a rock that as abundant white and dark minerals - a salt and pepper appearance.

Tuff

A relatively soft, porous rock that is usually formed by the compaction and cementation of volcanic ash or dust. Tuffs may be grouped as vitric, crystal, or lithic when they are composed principally of

glass, crystal chips, or the debris of pre-existing rocks, respectively. Some of the world's largest deposits of vitric tuff are produced by eruptions through a large number of narrow fissures rather than

from volcanic cones

WELDED TUFF

Welded tuff is a pyroclastic rock of any origin, that was

sufficiently hot at the time of deposition to weld together.

Strictly speaking, if the rock contains scattered pea-sized

fragments or fiamme in it, it is called a welded lapilli-tuff.

Welded tuffs (and welded lapilli-tuffs) can be of fallout

origin, or deposited from pyroclastic density currents, as in

the case of ignimbrites. During welding, the glass shards

and pumice fragments adhere together (necking at point

contacts), deform, and compact together, resulting in a

'eutaxitic fabric'.

BASALTIC TUFF

Basaltic tuffs are also of wide spread occurrence both in

districts where volcanoes are now active and in lands where

eruptions have long since ended. They are found in places,

where there are Palaeogene volcanic rocks. They are black,

dark green or red in colour; vary greatly in coarseness,

some being full of round spongy bombs a foot or more in

diameter.

RHYOLITE TUFF

Rhyolite tuffs contain pumiceous, glassy fragments and

small scoriae with quartz, alkali feldspar, biotite, etc. The

broken pumice is clear and isotropic, and very small

particles commonly have crescentic, sickle-shaped, or

biconcave outlines, showing that they are produced by the

shattering of a vesicular glass, sometimes described as

ash-structure. The tiny glass fragments derived from broken

pumice are called shards; the glass shards readily deform

and flow when the deposits are sufficiently hot, as shown in

the accompanying image of welded tuff.

Siltstone

Siltstone is a hardened sedimentary rock that is composed primarily of angular silt-sized particles (0.0039 to 0.063 mm [0.00015 to 0.0025 inch] in diameter) and is not laminated or easily split into

thin layers. Siltstones, which are hard and durable, occur in thin layers rarely thick enough to be classified as formations. Siltstone usually forms offshore, in quieter environments than the places that

make sandstone.

SILTSONE FOUND IN ESTONIA

20:12, 20 April 2005, this siltsone was found during an

geological expedition of the country. Siim Sepp, is an

Estonian, a geology student of the university of Tartu

took this photograph.

Due to a clay rich area for where this siltstone was

found, the reddish clay sits greatly contributed to the

color of this siltstone. Silstones color highly depends

on its environment thus silts may have different colors.

Some colors of siltstones are grey, white, yellowish

and brown.

PHYSICAL CHARACERISTICS

Siltstone, is highly rich in silts (98% of the stone) has a

grainy surface which gives it a fragile texture. Yet, this

kind of stone is commonly fairly hard and usually does

not split along flat planes.

Siltstones do not have a Mohs hardness. Relatively

speaking, however, some siltstones are relatively

easily broken due to its different silt composition.

SILTSTONE FOUND IN MOUNTAINSIDE

Siltstones is also one of the many types of gray stone

found in the mountainside, near rivers and shale,

sandstone and mudstone places.

The above picture was found in a mountain side of

Dong Nang Non, Thailand

Selenite

Selenite is a very common sedimentary mineral composed primarily of calcium sulfate dihydrate CaSO42H2O. It is one of evaporates rocks, formed when bodies of water evaporate leaving behind

chemicals that were dissolved in them. Lakes, rivers, oceans and ground water have all elemental chemicals dissolved in them. It is a form of gypsum. Selenite minerals are clear and colorless. It can

be translucent or transparent. It is very soft only a 2 on the Mohs scale of hardness, meaning selenite can be scratched with fingernail.

HOURGLASS SELENITE

Selenite is a crystallized form of gypsum. Gypsum is a

common mineral that takes on a great variety of crystal

forms and shapes. On the Salt Plains, the crystals are

formed just below the salt encrusted surface. They are

seldom found deeper than 2 feet below the surface.

Because these crystals form in wet soil, sand and clay

particles are included within the crystal. These

particles often form an "hourglass" shape inside the

crystal. This hourglass shape cannot be found in

selenite crystals in other places of the world; it is only

found here at the Salt Plains of NW Oklahoma.

SELENITE CLUSTER

Cluster of transparent selenite crystals. Some of these

crystals are water-clear, others have brown internal

inclusions. Mostly found in Naica Mine, Saucillo,

Chihuahua, Mexico. Selenite can form the largest

crystals in the world. In the Naica caves in Chihuahua,

Mexico single crystals can reach a length of 33 feet

and weigh over 55 tons.

GOLDEN SELENITE

Golden selenite that is from Naica Mine in Mexico.

Selenite mineral specimen with bladed crystal

terminations. The golden crystals exhibits translucency

due to the presence of other minerals or druse. Other

minerals intermixing with selenite gives the color since

selenite is clear and colorless. It can form large beds

hundreds of feet thick and covering many square

miles.

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be

regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable quantities of other elements,

chiefly hydrogen, sulfur, oxygen, and nitrogen.

LIGNITE

Sometimes called "brown coal," this is a brownish-

black coal with generally high moisture and ash

content and lower heating value. It is the geologically

youngest and lowest ranked coal. It contains 25 to 35

percent carbon and has the lowest heating value,

4,000 to 8,300 Btus per pound.

BITUMINOUS

Sometimes called "soft coal", this coal is 45 to 86

percent carbon, softer than anthracite, and has a heat

content between 10,500 and 14,000 Btus per pound.

ANTHRACITE

Sometimes called 'hard coal," this coal is 86 to 97

percent carbon and has the highest energy content of

all coals, nearly 15,000 Btus per pound.

Quartz Diorite

Diorite is a coarse-grained, intrusive igneous rock that is intermediate in composition between granite and gabbro. Its composition is very similar to the fine-grained extrusive rock known as andesite.

FIGURE 1

Quartz diorite is an igneous, plutonic (intrusive) rock of

felsic composition with phaneritic texture. Feldspar is

present as plagioclase (typically oligoclase or

andesine) with 10% less potassium feldspar. Quartz is

present at between 5 to 20% of the rock. Biotite,

amphiboles and pyroxenes are common dark

accessory minerals.

FIGURE 2

Diorite is composed primarily of plagioclase feldspar,

amphibole, and pyroxine minerals with small amounts

of biotite mica. It typically contains very little

quartz. When identifying diorite look for a rock that as

abundant white and dark minerals - a salt and pepper

appearance. With a hand lens, look for the cleavage

faces of plagioclase feldspar intersecting at oblique

angles. Also, look for vitreous cleavage faces on the

dark amphibole minerals.

FIGURE 3

Diorites may be associated with

either granite or gabbro intrusions, into which they may

subtly merge. Diorite results from partial melting of

a mafic rock above a subduction zone. It is commonly

produced in volcanic arcs, and in cordilleran mountain

building such as in the Andes Mountains as

largebatholiths. The extrusive volcanic equivalent rock

type is andesite.

Quartz (Massive)

Quartz is the second most abundant mineral in the Earth's continental crust, after feldspar. It is one of the most common rock-building minerals and is the reason why most rocks are hard. It is mostly

found in massive form, namely it is not in crystal form. Massive quartz exhibits a trigonal crystal system. It may appear colorless or in different colors like white, pink, rose, red and etc. It is very hard

having a Mohs hardness of 7. It is vitreous and leaves a white streak. It has no cleavage but has a conchoidal fracture. It is found either transparent or translucent and has a specific gravity range of

2.60-2.70 g/cm3.

ROSE QUARTZ

Rose quartz is a type of quartz that is pink in color

caused by trace amounts of manganese or titanium.

Ancients believed that it helps women have beautiful

complexion and that it prevents wrinkles.

QUARTZITE

Quartzite is a non-foliated metamorphic rock that is

produced by the metamorphism of sandstone. It is

composed primarily of quartz.

MILKY QUARTZ

A type of quartz that turned white due to bubbles and

liquids present during its formation. Its name comes

from the fact that its color looks like milk.

Magnetite

Magnetite is a mineral, one of the two common naturally occurring iron oxides (chemical formula Fe3O4) and a member of the spinel group. Magnetite is the most magnetic of all the naturally

occurring minerals on Earth.[6] Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, and this was how ancient people first noticed the property of magnetism.

MAGHEMITE

Maghemite exhibits ferrimagnetic ordering with a high

Nel temperature (~950 K), which together with its low

cost and chemical stability led to its wide application as

a magnetic pigment in electronic recording media

since the 1940s.

GOETHITE

Goethite is an iron bearing oxide mineral found in soil

and other low-temperature environments. Goethite has

been well known since prehistoric times for its use as

a pigment. Evidence has been found of its use in paint

pigment samples taken from the caves of

Lascaux in France.

CHESTERITE

Chesterite is a rare silicate mineral that can be

compared toamphiboles, micas, and jimthompsonite. It

was named after Chester, Vermont, where it was first

described in 1977. The specific geologic setting within

its origin is the Carleton talc quarry in Chester,

Vermont.

Jade

Jade is best known as a green ornamental stone. Its colors vary from light to dark green, but it may also be other colors such as white, gray, and purple. Jade is actually the gemstone name for two

different mineral forms, Jadeite and Nephrite. These two minerals can be identical in appearance and are similar in their physical properties, and until modern times no distinction was made between

the two different types of Jade. While Nephrite is generally only green, cream, or white, Jadeite colors can range through the color spectrum with more exotic colors.

JADEITE

Jadeite is made up of interlocking granular pyroxene

crystals. It occurs in a wide range of colors, such as

green, lilac, white, pink, brown, red, blue, black,

orange and yellow. It has a dimpled surface when

polished. The most prized variety, imperial jade, is a

deep rich emerald green due to chromium content

CHLOROMELANITE

Chloromelanite is a type of jadeite. Its color ranger

from dark green to black.

NEPHRITE

Nephrite is found as aggregates of fibrous amphibole

crystals. Its composite forms an interlocking structure

that are tougher than steel. Its colors may vary from a

dark green (which is rich in iron) to a cream color

(which is high in magnesium). It may be homogeneous

in color, banded or blotchy.

Anhydrite

Anhydrite is a sedimentary mineral composed of calcium, sulfur, and oxygen. It is also known as calcium sulfate. Good specimens of natural anhydrite are often sought by mineral and rock collectors.Anhydrite is usually white, colorless, or gray. It can also be found with violet or blue tones. When it has a soft blue color it may be referred to as angelite. Scratching the mineral on a streak plate usually results in white residue. It is relatively soft, only rating 3.5 on the Mohs hardness scale..

BLUE ANHYDRITE

Angelite or Blue Anhydrite is a fairly new discovery in the gem and mineral world. Discovered in 1987 in Peru, during the Harmonic Conversion, it's colors may be white, gray or colorless, as well as blue to violet. The most common color is a blue-gray color that most stones for jewelry are created in. Blue is the color of the present time, the Aquarian Age. The Aquarian is seen as the truth seeker; however, she or he must go forward in truth, for if they do not go forward, they will go backwards out of fear. Angelite combats this fear.It will help you unlock the secrets of the spoken word, giving voice to your truth. Psychologically, angelite counteracts harshness; if somebody is acting insensitively in a situation, angelite will help that person to become more compassionate. It also teaches them acceptance of that which cannot be changed.

SATIN SPAR GYPSUM

Gypsum (CaSO4.2H2O) and anhydrite (CaSO4) are two related minerals formed in Indiana during periodic episodes of ancient sea water evaporation in restricted basins. Large deposits of both minerals are located in northwestern and southwestern Indiana.These deposits are commonly associated with dolostone and limestone. Anhydrite may be converted to gypsum with the addition of the water accompanied by a volume increase that destroys any planar features in the beds. The reverse is also possible, creating anhydrite by dehydrating gypsum.Both minerals display vitreous luster and are white in color and streak. The calcium in either mineral may besubstituted by small amounts of strontium and barium. The differences in their physical characteristics help toidentify these minerals. Gypsum is a soft mineral that can be scratched with your fingernail and has four differentcleavage surfaces. Its crystals display a variety of forms, the most common being a granular, massive rockknown as alabaster Aggregates of fibrous gypsum form a variety called satin spar.

FIGURE 3

Shale

Shale is a fine-grained sedimentary rock that forms from the compaction of silt and clay-size mineral particles that we commonly call "mud". This composition places shale in a category of

sedimentary rocks known as "mudstones". Shale is distinguished from other mudstones because it is fissile and laminated. "Laminated" means that the rock is made up of many thin layers. "Fissile"

means that the rock readily splits into thin pieces along the laminations. Shale is the most abundant sedimentary rock and is in sedimentary basins worldwide.

BARNETT SHALE

The Barnett shale is an organic and silica-rich black mudstone of middle to late Mississippian age. Long considered the probable source rock for several regional oil and gas reservoirs, it is located in the Forth Worth Basin of north-central Texas. The basin is bounded to the east by the Ouachita fold and thrust belt, to the north by basement uplift arches, to the west by the Bend arch, and to the south by the Llano uplift. Open fractures and faults are rare within the Barnett, with nearly all fractures seen in core and logs filled with calcite. The Barnett shale consists of siliceous organic-rich mudstone, limestone, and minor dolomite. The shale intervals generally contain high silica (35-50%), relatively low clay (

Serpentinite

Serpentinite is composed dominantly of the serpentine minerals (chemical formula MgSiO (OH) ). It is green to dark green coloured. It is usually formed by alteration of ultramafic rocks, such as

dunites and peridotites by a process called serpentinization. It is common beneath the oceanic crust, where it forms by the alteration of the mantle rock peridotite. But it is seldom seen on land

except in rocks from subduction zones, where oceanic rocks may be preserved. Most people call it serpentine (SER-penteen) or serpentine rock, but serpentine is the set of minerals that make up

serpentinite (ser-PENT-inite). It gets its name from its resemblance to snakeskin, with a mottled color, waxy or resinous luster and curving, polished surfaces.

SERPENTINE (CHRYSOTILE)

Chrysotile is a mineral of the serpentine group that

crystallizes in thin, flexible fibers. As you can see on this

specimen from northern California, the thicker the vein, the

longer the fibers. It is one of several different minerals of

this type, suitable for use as fireproof fabric and many other

uses, that together are called asbestos. Chrysotile is the

dominant form of asbestos by far, and in the home it is

generally harmless although asbestos workers must beware

of lung disease due to chronic overexposure to the fine

airborne fibers of powdered asbestos. A specimen like this

is completely benign.

SERPENTINE (ANTIGORITE)

Antigorite (a magnesium iron hydroxysilicate), like amesite,

is a member of the serpentine subfamily of phyllosilicates -

this large miniature cluster of silky green antigorite is from

the Jeffrey Quarry, Asbestos, Qubec, Canada.

CHRYSOTILE ASBESTOS ORE

Chrysotile asbestos is the fibrous form of the mineral

lizardite of the serpentine group of minerals. Its chemical

formula is Mg3[Si2O5](OH)4 with some Fe2+ substituting for

Mg. The amount of iron substitution affects the refractive

indices and the birefringence. This is the most common

form of asbestos used commercially, comprising about 93%

of all the asbestos mined. It is also the least hazardous of

the asbestos minerals. It is the most flexible of the asbestos

minerals and is the one typically used in making asbestos

cloth and asbestos paper.

Sandstone

Sandstone is a sedimentary rock consisting of sand or quartz grains cemented together, typically red, yellow, or brown in color. The sediment particles are clasts, or pieces, of minerals and fragments of rock, thus sandstone is a clastic sedimentary rock. It is composed mostly of sand, which means particles of a medium size, so sandstone is a medium-grained clastic sedimentary rock. More precisely, sand is between 1/16

millimeter and 2 mm in size (silt is finer and gravel is coarser). Sandstone may include finer and coarser material and still be called sandstone, but if it includes more than 30 percent grains of gravel, cobble or boulder

size it's classified instead asconglomerate or breccia (together these are called rudites).

MICAS

Micas are significant rock forming minerals being

found in all three rock types: igneous, metamorphic

and sedimentary. Because thin flakes of mica are

generally flexible and brittle, it is surprising how

resistant and durable mica crystals can be in

withstanding high temperatures and pressures in

metamorphic regimes as well as the punishment of

erosional environments. The term "mica" is so familiar

to the general public that it is often considered a

mineral in itself.

PHYLLOSILICATE SUBCLASS

In the Phyllosilicates, rings of tetrahedrons are linked

by shared oxygens to other rings in a two dimensional

plane that produces a sheet-like structure. The typical

crystal habit of this subclass is flat, platy, book-like and

most all members display good basal cleavage.

Although members tend to be soft, they are

remarkably resilient. Members of this group are often

the last to chemically breakdown in erosional and

weathering processes and thus constitute a significant

amount of soils and fine grained sedimentary rocks.

This group is also generally tolerant of high pressures

and temperatures and they make-up a large part of

metamorphic rocks.

FELDSPAR

The feldspars are a group of minerals that have similar

characteristics due to a similar structure. All feldspars

have low symmetry, being only monoclinic, 2/m, to

triclinic, bar 1. They tend to twin easily and one crystal

can even be multiply twinned on the same plane,

producing parallel layers of twinned crystals. They are

slightly hard at around 6, and have an average density

at 2.55 to 2.76. They have a rather dull to rarely

vitreous luster. Crystals tend to be blocky. Some

feldspars may be triboluminescent. They have two

directions of cleavage at nearly right angles. Feldspars

also tend to crystallize inigneous enviroments, but are

also present in many metamorphic rocks.

Marble

Marble is a non-foliated metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Geologists use the term "marble" to refer to metamorphosed limestone;

however, stonemasons use the term more broadly to encompass unmetamorphosed limestone. Marble is commonly used for sculpture and as a building material.

SWEDISH GREEN MARBLE

Swedish green marble is a marble from the quarries of

Kolmarden in Sweden. It is fine-grained, with a

variable green color due to serpentines in the stone. It

is considered as one of the hardest marbles in the

world.

SIENNA MARBLE

Sienna marble is quarried in Northern Italy in areas

around town with the same name. It is one of the most

beautiful of all the marbles having a color range from

violet, red, blue and white.

CREOLE MARBLE

Creole marble is a marble from quarries in Pickens

County, Georgia. It is coarse-grained, displays a white

or gray background while veins or clouds are black or

dark blue. Based on the tone and coloring, it is sold as

Light Creole, Medium Creole, and Dark Creole.

Jasper

The name Jasper is derived from the Greek word iaspi meaning ''spotted stone.'' It is a form of chalcedony that may contain up to 20 percent foreign materials or inclusions, including organic material

and mineral oxides, which determine the color, pattern and appearance of the stone. Uniformly colored jasper is rare; usually it is multicolored, spotted or banded. It is an opaque form of Chalcedony,

which is a microcrystalline variety of the mineral Quartz. It often contains an abundance of impurities, and therefore some regard it as a rock instead of a mineral. Jasper is usually associated with

brown, yellow, or reddish colors, but may be used to describe other opaque colors of Chalcedony such as dark or mottled green and orange. Some forms of Jasper are banded, and these banded

Jaspers may appear similar to Agate

BRECCIATED RED JASPER

Brecciated Red Jasper in rounded fragments naturally

cemented together in a gray material; appears similar to

breccia. It has a higher content of hematite and the veins

are clearly visible across this mineral. Occasionally it also

includes bands of quartz.

HELIOPTROPE JASPER

Helioptrope Jasper is a dark green, opaque jasper with

small red spots rich in iron oxides. Heliotrope is also known

as bloodstone, but should not be confused with hematite

which is named for its blood-red streak. The deep green

color can be caused by various embedded minerals of

microscopic size, as like chlorite or actinolite. The green

parts of heliotrope are practically opaque. The red spots are

colored by embedded hematite, Fe2O3

DALMATIAN JASPER

Dalmatian Jasper has a Trigonal crystal system and is the mineral class of oxide in the Quartz group. Basically, most Jaspers are fine grained Quartz that holds lots of foreign materials.

Dalmatian Jasper forms in a sedimentary manner when the original silicic acid solution seeps into sandy rock and becomes saturated with lots of suspended particles. The orange color spots come from iron, the darker black to brown spots can be anything from old plant material to old sea bottom materials (shells, etc.). The pale yellow background comes from finely ground clay and sand particles. Dalmatian Jasper can be found world-wide.

Gneiss

Gneiss is an old German word meaning bright or sparkling. Gneiss is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains. It typically contains

abundant quartz or feldspar minerals. It is a rock of great variety with large mineral grains arranged in wide bands. It means a type of rock texture, not a composition.

LEWISIAN GNEISS

Lewisian Gneiss is a suite of Precambrian metamorphic

rocks that outcrop in the northwestern part of Scotland,

forming part of the Hebridean Terrane. These rocks are of

Archaean and Paleoproterozoic age, ranging from 3.01.7

Ga. They form the basement on which the Torridonian and

Moine Super group sediments were deposited. The

Lewisian consists mainly of granitic gneisses with a minor

amount of supracrustal rocks. Rocks of the Lewisian

complex were caught up in the Caledonian orogeny,

appearing in the hanging walls of many of the thrust faults

formed during the late stages of this tectonic event.

ACASTA GNEISS

The Acasta Gneiss is a rock outcrop of Hadean tonalite

gneiss in the Slave craton in Northwest Territories, Canada.

Located on an island about 300 kilometres north of

Yellowknife, the Acasta River rock deposit, believed to be

4.031 to 3.58 billion years old, is the oldest known intact

crustal fragment on Earth. Found in 1989, it was named for

the nearby Acasta River east of Great Bear Lake. The

Acasta outcrop is found in a remote area of the Tlicho

people land settlement. It is the oldest known exposed rock

in the world. The rock exposed in the outcrop is derived

from a 4.2 billion year old granitoid; an age based on

radiometric dating of zircon crystals at 4.2 Ga. The Acasta

Gneiss is important in establishing the early history of the

continental crust. It was formed in the Basin Groups

unofficial period of the Hadean eon, which came before the

Archean.

AUGEN GNEISS

Augen (from German "eyes") is large, lenticular eye-shaped

mineral grains or mineral aggregates visible in some

foliated metamorphic rocks. In cross section they have the

shape of an eye. Augen form in rocks which have

undergone metamorphism and shearing. The core of the

augen is a porphyroblast or porphyroclast of a hard,

resilient mineral such as garnet. The augen grows by

crystallization of a mantle of new mineral around the

porphyroblast. The mantle is formed contiguous with the

foliation which is imparted upon the rock, and forms a

blanket which tapers off from either side of the

porphyroblast within the strain shadows. A metamorphic

rock which is clotted with augen is often called an augen

gneiss. A long wall of this augen gneiss can be felt at the

Mineral and Lapidary Museum of Western North Carolina.

Breccia

Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can

be filled with a matrix of smaller particles or mineral cement that binds the rock together.

Breccia forms where broken, angular fragments of rock or mineral debris accumulate. One possible location for breccia formation is at the base of an outcrop where mechanical weathering debris

accumulates. Another would be in stream deposits near the outcrop such as an alluvial fan. Some breccias form as debris flow deposits. The angular particle shape reveals that they have not been

transported very far (transport wears the sharp points and edges of angular particles into rounded shapes). After deposition the fragments are bound together by a mineral cement or by a matrix of

smaller particles that fills the spaces between the fragments.

LIMESTONE BRECCIA

A breccia that contains clasts of multiple types of limestone.

Specimen is about four inches (ten centimeters) across.

CHERT BRECCIA

The angular clasts in this breccia are chert fragments. The

matrix is an iron-stained mix of clay through sand-size

particles. The specimen is about two inches (5cm) across.

IMPACT BRECCIA

A 457.7-gram breccia specimen from the Popgai impact

crater in northern Siberia. Note the variety of colors, sizes,

shapes and textures within a single massthe result of a

major meteorite impact which threw millions of tons of rock

into the air. As fragments fell back to earth, rocks from

different strata were mixed together.

Gabbro

Gabbro is a coarse-grained, dark-colored, intrusive igneous rock. It is usually black or dark green in color and composed mainly of the minerals plagioclase and augite. It is the most abundant rock in

the deep oceanic crust. Gabbro has a variety of uses in the construction industry. It is used for everything from crushed stone base materials at construction sites to polished stone counter tops and

floor tiles.

FIGURE 1

Essexite is also called nepheline monzogabbro is a

dark gray or black holocrystalline plutonic igneous

rock. Its name is derived from the type locality in Essex

County, MA. It contains plagioclase as the

dominant feldspar, as well

as orthoclase feldspar, augite, biotite,hornblende, olivi

ne, and nepheline. As the proportion of nepheline

increases, essexite grades intotheralite.

FIGURE 2

This gabbro has a lot of coarse, dark pyroxene crystals

in it. There is also a lot of plagioclase, but it is tough to

spot because it is also quite dark. The shiny cleavage

planes in the upper part of this sample are all

plagioclase.

FIGURE 3

This typical gabbro is made of pyroxene and

plagioclase, but it is tough to see really good features

of either mineral

Diabase

Diabase, also called Dolerite, is a common igneous rock which is mainly composed of calcium-rich plagioclase feldspar and pyroxene. It is usually found in smaller relatively shallow intrusive bodies

such as dikes and sills. This rock solidified from a basaltic magma within a few hundred meters of the surface, probably beneath a volcano. It cooled rapidly, giving it a fine-grained, peppery

appearance. Diabase is an extremely hard rock, making it difficult to carve and work with.

KORPI BLACK

The black diabase Korpi Black is a fine grained

granite-like natural stone from Finland. As a diabase,

Korpi Black is most likely suitable for applications

as gardening decoration, and sillier usages.

COBBLESTONE

Cobblestones are stones that were frequently used in

the pavement of early streets. "Cobblestone" is derived

from the very old English word "cob", which had a wide

range of meanings, one of which was "rounded lump"

with overtones of large size. "Cobble", which appeared

in the 15th century, simply added the diminutive suffix

"le" to "cob", and meant a small stone rounded by the

flow of water; essentially, a large pebble. It was these

smooth "cobbles", gathered from stream beds, which

paved the first "cobblestone" streets.

PRESELI SPOTTED DOLERITE

This metamorphosed dolerite comes from the Preseli

Mountains, Pembrokeshire, Wales. It is particularly

notable for its spotted appearance in hand specimen,

an effect caused by low grade regional metamorphism

during the Caledonian orogeny. This rock and its

location are particularly important to the history of the

United Kingdom because the same rock was used to

build Stonehenge, over 200 km to the east.

Schist

Schist is a coarse grained metamorphic rock. Shale is the parent rock. It is made up of clay minerals. Shale can metamorphose into slate, phyllite,schist or gneiss depending on the degree of heat and pressure. Schist has a greater degree of metamorphism than phyllite but less than gneiss. It is classed as a medium-grade metamorphic rock and is associated with regional metamorphism do to mountain building. The crystals in schist are large enough to see with the naked eye. They are flattened and elongated. Schist contains more than 50% platy and elongated minerals. Schist is foliated or layered in appearance. Quartz, micas, and amphiboles are primary minerals in schist. Schist comes from a Greek word meaning "to split"

GREEN SCHIST

Greenschist are metamorphic rocks that formed under the

lowest temperatures and pressures usually produced by

regional metamorphism, typically 300450 C (570840 F)

and 14 kilobars (14,50058,000 psi).[1] The name comes

from commonly having an abundance of green minerals

such as chlorite, serpentine, and epidote, and platy

minerals such as muscovite and platy serpentine. The

platiness causes the tendency to split, or have schistosity.

MANHATTAN SCHIST

Manhattan Schist is Devonian in age. It has undergone at

least 4 well-defined stages of deformation and is very

strongly deformed in most exposures. The photo shows a

glacially smoothed surface exhibiting parallel glacial

striations. Bands of pegmatite are visible in the photograph

(and in the second closeup photo). Summit Rock, the

highest point in Central Park, located between 83rd-84th

Streets along Central Park West, is composed of Manhattan

Schist.

MEDIUM-GRADE SCHIST

This view is of the flat cleavage surface of a medium-grade

schist. The rock has a purplish sheen because both dark

mica (biotite) and light mica (muscovite) are present. It is

just coarse enough to distinguish individual mica flakes, and

some of them are reflecting the light from the illuminating

lamps and appear as white specks. Also visible are large

dull red-brown garnet crystals up to 1 cm across.

Chert Chert is a microcrystalline or cryptocrystalline sedimentary rockmaterial composed of silicon dioxide (SiO2). It occurs as nodules, concretionary masses and as layered deposits. Chert breaks with a

conchoidal fracture, often producing very sharp edges. Early people took advantage of how chert breaks and used it to fashion cutting tools and weapons. It varies greatly in color (from white to

black), but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements present in the rock, and both red and green are most often

related to traces of iron (in its oxidized and reduced forms respectively).

FLINT

Flint is a hard, sedimentary cryptocrystalline form of

the mineral quartz, categorized as a variety of chert. It

occurs chiefly as nodules and masses in sedimentary

rocks, such as chalks and limestones. Inside the

nodule, flint is usually dark grey, black, green, white, or

brown in colour, and often has a glassy or waxy

appearance. A thin layer on the outside of the nodules

is usually different in colour, typically white and rough

in texture. From apetrological point of view, "flint"

refers specifically to the form of chert which occurs in

chalk or marly limestone. Similarly, "common chert"

(sometimes referred to simply as "chert") occurs in

limestone.

JASPER

Jasper is a variety of chert formed as primary deposits,

found in or in connection with magmatic formations

which owes its red color to iron(III) inclusions. Jasper

frequently also occurs in black, yellow or even green

(depending on the type of iron it contains). Jasper is

usually opaque to near opaque.

RADIOLARITE

Radiolarite is a variety of chert formed as primary

deposits, found in or in connection with magmatic

formations which owes its red color to iron(III)

inclusions. Jasper frequently also occurs in black,

yellow or even green (depending on the type of iron it

contains). Jasper is usually opaque to near opaque.

Conglomerate

Conglomerate is a sedimentary rock formed from rounded gravel and boulder sized clasts cemented together in a matrix. The rounding of the clasts indicates that they have been transported some

distance from their original source (e.g. by a river or glacier), or that they have resided in a high energy environment for some time (e.g. on a beach subject to wave action). The cement that binds the

clasts is generally one of either calcite, silica or iron oxide. The matrix can consist solely of the cementing material, but may also contain sand and / or silt sized clasts cemented together among the

coarser clasts. Conglomerates can be further divided according to: Class - conglomerate can be divided into two broad classes: Clast supported - where the clasts touch each other and the matrix fills

the voids; and Matrix supported - where the clasts are not in contact and the matrix surrounds each clast; Clast size - fine (2 - 6mm), medium (6 - 20mm), coarse (20 - 60mm), very coarse (> 60mm).

PETROMICT CONGLOMERATE

If the phenoclasts include a lot of a fresh metastable

rock types of conglomerate is called petromict. The

dark stones in this beach exposure of the San Onofre

Breccia are andesitic lava.

OLIGOMICT CONGLOMERATE

If the phenoclasts come from a few different parent

rocks the conglomerate is called oligomict (ALL-

igomict). Because the matrix and phenoclasts differ in

their composition the conglomerate is called

extraformational.

MONOMICT CONGLOMERATE

If all the phenoclasts come from the same parent rock

the conglomerate is called monomict. If the matrix and

phenoclasts come from the same parent the

conglomerate is called intraformational.

Chalcopyrite

Chalcopyrite (or copper pyrite), looks like, and is easily confused with Pyrite, FeS2. Chalcopyrite is one of the minerals refered to as "Fool's Gold" because of its bright golden color. But real gold is a

more buttery yellow and is ductile and malleable.

QUARTZ

Quartz is the most common mineral found on the

surface of the Earth. A significant component of many

igneous, metamorphic and sedimentary rocks, this

natural form of silicon dioxide is found in an impressive

range of varieties and colours. There are many names

for different varieties. Cryptocrystalline varieties of

quartz are listed separately under chalcedony, and

include agate.

MONCHEITE CHALCOPYRITE

White mocheite with chalcopyrite (orange, blue and violet

tarnishing colors) in silicate matrix. Polished section (from

microphone analysis) in reflected light.

TELARGPALITE CHALCOPYRITE

Gray long-prismatic crystal of oulankaite with light grayish

telargpalite and pale yellowish-white rims of tulameenite in

massive yellowish chalcopyrite. Polished section (from

microprobe analysis) in reflected light.

Biotite Biotite is a common phyllosilicate mineral within the mica group. More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the

magnesium-endmember phlogopite; more aluminous endmembers include siderophyllite. Biotite is a sheet silicate. Iron, magnesium, aluminium, silicon,oxygen, and hydrogen form sheets that are

weakly bound together by potassium ions. It is sometimes called "iron mica" because it is more iron-rich than phlogopite. It is also sometimes called "black mica" as opposed to "white mica"

(muscovite) both form in some rocks, in some instances side by side.

MEROXENE SOMMA

Like other mica minerals, biotite has a highly perfect basal cleavage, and consists of flexible sheets, or lamellae, which easily flake off. It has a monoclinic crystal system, with tabular toprismatic crystals with an obvious pinacoid termination. It has four prism faces and two pinacoid faces to form a pseudohexagonal crystal. Although not easily seen because of the cleavage and sheets, fracture is uneven. It appears greenish to brown or black, and even yellow when weathered. It can be transparent to opaque, has a vitreous to pearly luster, and a grey-white streak. When biotite is found in large chunks, they are called books because it resembles a book with pages of many sheets.

BIOTITE IN PLAIN POLARIZED LIGHT

Biotite displays perfect cleavage in one direction. The maximum absorption color is shown when the polarizer is parallel to the cleavage. Under crossed polars biotite displays a distinctive mottled texture as it nears extinction. In extinction position small spots fail to extinguish. These traits are charicteristic of birdseye extinction which is common in micas. In plane polarized light, biotite is seen as as dark brown to grey against the surrounding mostly colorless minerals. Under crossed polars "bird's eye extinction" can easily be seen when the mineral is nearly extinct. Often, the mineral color masks the interference colors when the mineral is not extinct.

BIOTITE IN PLAIN LIGHT

In plain light, biotite in a granite appears a slightly drab brown. Radiation damage from zircon can leave pleochroic spots that fade to extinction at a different rate that the surrounding, undamaged material. There are several small opaque grains as well. Under polarized light biotite appears green with pink undertones. It is surrounded by quartz and feldspars. This is an image of a thin section containing biotite. It is seen now in plane polarized light as a brown to tan color. Under cross-polarized light, the biotite thin section appears darker brown in areas as

well as a pink-yellow color in others.

Chromite

A brownish-black mineral that consists of a mixed oxide of chromium and iron and is the principal ore of chromium.

FIGURE 1

Relatively hard, metallic, black OXIDE MINERAL of

chromium and iron that is the chief commercial source

of chromium. Chromite is commonly found as brittle

masses in perdotites, serpentines, and other basic

igneous and metamorphic rocks. The principal

producing areas are South Africa, Russia, Albania, the

Philippines, Zimbabwe, Turkey, Brazil, India, and

Finland.

FIGURE 2

FIGURE 3