NON-SILICATES

Non Silicates• Native Elements

• minerals comprised of atoms of only one element• 1. metals

• minerals with high heat and electrical conductance, malleability, ductility and a strong metallic bond

• Au, Ag, Cu, Pt, etc.• 2. semi metals

• minerals with lesser conductivity but more brittle than metals and consist of a mixture of metallic and covalent bond types

• Sb, Bi and As• 3. non metals

• minerals which are non conductors, are very brittle and soft and have a covalent type of bond

• C (graphite), S (sulfur)

• Sulfides, Arsenides, Sulfarsenides• minerals with strong metallic bond type with a general formula,

AmXp, where X is S or As, Sb, Bi and Te and A represents one or more metals

• sulfides--S is the only major anion• arsenides--As takes the place of S totally ( NiAs)• sulfarsenides—semimetals take place of S in part (FeAsS)

• many of these minerals are known as “primary minerals” or those formed from hydrothermal solutions with no oxidation during formation

• examples are:• chalcocite—resembles enargite but has no cleavage• bornite—peacock ore—displays a tarnish and can resemble

covellite but does not have cleavage• galena –very high specific gravity with cubic cleavage and the

only source of lead

• sphalerite• comprised of Fe and Zn• resinous to adamantine• yellowish to deep red(ruby ore) to black(jack) indicating

a progressively higher Fe content• used as a geothermal mineral—the higher the Fe

content, the higher the temperature of formation• most important ore of Zn and an important source of

Cd• leaves a rotten egg smell when rubbed on a porcelain

scratch plate• chalcopyrite

• distinguished from pyrite in that it has no cleavage and is softer than glass

• distinguished from millerite in that it has no radiating crystal habit

• distinguished from pyrrhotite in that it is not magnetic• “ “ marcasite in that it has no cockscomb structure

• pyrrhotite• magnetic caused by omission solid solution and a defect

structure caused by an Fe deficiency with respect to S in the formula

• niccoline (niccolite)• red-brass colored with a high specific gravity

• millerite • hair like radiating crystal habit

• pentlandite• resembles pyrrhotite but not magnetic• principle ore of Ni

• covellite• also known as peacock ore, with special iridescence• excellent cleavage resembling that of mica• indigo color

• cinnabar• red, high specific gravity with prominent cleavage• most important ore of Hg

• realgar• red and associated with orpiment

• orpiment• yellow and distinguished from S by its prominent

cleavage• pyrite

• harder than chalcopyrite • occurs often in cubic cleavage form with striations• most common sulfide minerals• commonly known as fool’s gold

• marcasite• a polymorph with pyrite • differs from pyrite by the presence of the cockscomb

structure

• molybdenite• distinguished from graphite by a higher specific gravity

and more bluish tone• principal ore of Mo

• arsenopyrite• distinguished from marcasite by its somewhat silver-

white color• principal source of As

• Sulfosalts• have general formula, AmBnXp where A can be Ag, Cu, Pb and

B can be As, Sb,Bi and X is S• the semimetals act as cations in the sulfosalts as compared to

anions in the sulfarsenides and arsenides• an example is:

• enargite• distinguished from chalcocite by its prominent cleavage

• Oxides• bond type is primarily ionic which results in part to a greater

hardness displayed by these compared to others previously discussed

• examples are: • cuprite

• in various shades of red

• zincite• red and occurs often with franklinite

• Hematite group• isostructural group—6 O bonded to each cation and 4 anions bonded to

each cation (e.v. of bond = ½)• examples are:

• corundum • hardness = 9• sapphires (blue) and rubies (red) are important gem stone

varieties• hematite

• occurs often as oolitic hematite (non metallic luster) or specularite or massive hematite (both metallic luster)

• most important ore of iron• ilmenite

• distingushed from magnetite from lack of strong magnetism• The major source of Ti

• Rutile group• isostructural group with 6 O around each cation and 3

cations around each O• examples are:

• rutile• much lower S.G. than cassiterite• adamantine luster and reddish color

• pyrolustite• low hardness and leaves a black streak on paper• most important Mn ore

• cassiterite• very high S.G.• principal ore of Sn

• Spinel group• isostructural group—first cation in formula is +2 and

second is +3• examples are:

• magnetite• very magnetic

• chromite• massive to granular• distinguished from magnetite by lack of magnetism• the only abundant ore of Cr

• franklinite• distinguished from magnetite by lack of strong

magnetism• is abundantly associated with zincite

• Hydroxides• examples are:

• brucite• distinguished from talc by a greater hardness and lack

of a strong greasy feel• manganite

• distinguished from pyrolusite and other black mineral by its brown streak

• often occurs in prismatic crystals• romanechite (psilomelane)

• black and occurs often in botryoidal form• goethite

• black and often oxidizes to limonite (yellow)• bauxite

• recognized by its pisolitic form—most important ore of Al

• Halides• consists of minerals with a halogen anion• examples are:

• halite• distinguished by its cubic cleavage and salty taste which

is less bitter than taste of sylvite• cryolite• fluorite

• often found in cubes and in various colors• has distinct octahedral cleavage• is an important source of F in the production of HF

• Carbonates• The remaining non silicate classes are comprised of minerals

each combined with a meso-or aniso and isodesmic bond• Calcite group

• isostructural group 6 O around each major cation, 3 O around C and 1 C and 2 other major cations around each O

• examples are:• calcite

• prominent rhombohedral cleavage and often found as rhombohedron or scalenohedron(dog tooth) forms

• distinguished from other minerals by strong effervescence with cold HCl in a solid non powered form

• magnesite• prominent rhombohedral cleavage but rare and

usually white and very fine grained

• siderite• prominent rhombohedral cleavage with curved faces• distinguished from other carbonates by its light to dark

brown color and from sphalerite by its type of cleavage and lack of smell of rotten eggs on a streak plate

• rhodochrosite • prominent rhombohedral cleavage with curved faces

and pink color• smithsonite

• blue-green in color and botryoidal or stalactitic in form• Aragonite group

• isostructural group with 9 Oaround each major cation, 3 O around each C, and 1 C and 3 major cations around each O

• aragonite• polymorphic with calcite • distinguished from calcite by the lack of rhombohedral

cleavage and from witherite and strontionate by its much lower S.G.

• witherite• high S.G. • distinguished from barite by its effervescence in cold

HCl in powered form• Dolomite group

• isostructural group similar to the calcite group• example is:

• dolomite• often displays curved rhombohedral cleavage• effervesces in HCl in power form only

• Hydrous Carbonate group• examples are:

• malachite• distinguished by its bright green color and

botryoidal form• effervesces with cold dilute HCl yeilding a green

solution• azurite

• distinguished by its azure blue color and effervescence with cold HCl yielding a blue solution

• Borates• there is a polmerization of the basic structural units as in the

silicates because of the presence of the mesodesmic bond• borates are the source of borax and B

• examples are:• kernite

• characterized by its long splintery cleavage fragments and slow solubility in cold water

• can resemble gypsum but is harder and cannot be scratched by the fingernail

• borax• characterized by its crystals and its low hardness

resulting in powdery form• easily soluble in cold water

• colemanite• commonly found in short prismatic crystals

• Sulfates• Barite group

• isostructural group with 12 O around each major cation, 4 O around each S, and 1 S and 3 major cations around each O

• an example is:• barite

• distinguished by its prominent cleavage, high S.G. and often by the special crystal forms as bladed barite, clear barite, rose barite and a black barite

• chief source of Ba• anhydrite

• not isostructural with barite---8 O around each Ca, 4 O around each S and 1 S and only 2 Ca around each O

• 2 directional 90 degree cleavage

• Hydrous Sulfate group• examples are:

• gypsum• characterized by its low hardness (2) and 3 cleavage

directions• can occur in several forms as bladed gypsum,

selenite (clear), satin spar and massive or alabaster• alunite

• Tungstates• wolframite group is an isostructural group • an example is:

• wolframite• distinguished from other minerals by its black color, one

directional cleavage and high S.G. • an important ore of W

• Molybdates• an example is:

• wulfenite• characterized by its orange-yellow color, high S.G. and

tabular (tetragonal) crystals

• Vanadates• an example is:

• vanadinite• characterized by its ruby red to orange red color,

resinous luster and high S.G.• Phosphates

• examples are:• monazite

• rare earth phosphate with high S.G. and main source of Th and other rare earth elements

• apatite• green, red and yellow apatite are varieties

• amblygonite• distinguished from sodic plagioclase by the lack of

striations • wavelite

• commonly in radiating crystal form and green in color• turquoise

• distinguished by its color and harder than chrysocolla