MINERALOGYMINERALOGYBranch of Geology that deals with the Branch of Geology that deals with the

study of Mineralsstudy of MineralsThe Solid crust of the earth is made up of The Solid crust of the earth is made up of

rocks. Rocks are aggregates of mineralsrocks. Rocks are aggregates of mineralsThe property of a rock is in turn based on The property of a rock is in turn based on

the property of the Minerals present in it, the property of the Minerals present in it, based on which it can be used suitably.based on which it can be used suitably.

Atoms combine to form Atoms combine to form ElementsElements

ElementsElements – fundamental component that – fundamental component that can not be broken down into other can not be broken down into other substances by ordinary chemical substances by ordinary chemical processesprocesses

Elements combine to form mineralsElements combine to form minerals

General Facts About MineralsGeneral Facts About Minerals

5,000 + minerals have been identified5,000 + minerals have been identified

A few are “native elements” -- made of A few are “native elements” -- made of only one element, such as sulfur, gold. only one element, such as sulfur, gold. copper, and graphite (carbon)copper, and graphite (carbon)

Most are compounds, especially the Most are compounds, especially the silicate group (Si, O).silicate group (Si, O).

Other important groups are oxides, Other important groups are oxides, carbonates, and sulfides.carbonates, and sulfides.

Gold (Au)Silver (Ag)Platinum (Pt)Diamond (C)Graphite (C)Sulfur (S)Copper (Cu)

MINERALS

NATIVE ELEMENTS

Copper

Silver

Gold

Mineral CriteriaMineral Criteria1. Naturally occurring – not manufactured 1. Naturally occurring – not manufactured

2.Are Solids2.Are Solids

3.Inorganic – minerals not made by living things (organic)3.Inorganic – minerals not made by living things (organic)

4.Crystalline solid – atoms have specific arrangement or 4.Crystalline solid – atoms have specific arrangement or crystal structure crystal structure

5.5. Have a definite chemical composition – may be a single Have a definite chemical composition – may be a single element or combinationelement or combination

MINERAL FORMATIONMINERAL FORMATIONCRYSTALLIZE FROM MAGMA or LAVACRYSTALLIZE FROM MAGMA or LAVA

solidification of liquid magma/lava to solid solidification of liquid magma/lava to solid with a definite internal arrangement of with a definite internal arrangement of atoms into a regular repeating patternatoms into a regular repeating pattern

PRECIPITATE FROM SOLUTIONPRECIPITATE FROM SOLUTION dissolved minerals come out of solution dissolved minerals come out of solution (water) to form solids (water) to form solids

Minerals are identified by their Minerals are identified by their Physical Properties Physical Properties

ColorColorStreakStreakLuster – metallic, non-metallic Luster – metallic, non-metallic Hardness – Mohs Hardness Scale (1-10)Hardness – Mohs Hardness Scale (1-10)CleavageCleavageFractureFractureCrystal Form – determines physical propertiesCrystal Form – determines physical propertiesTenacityTenacityDiaphaneityDiaphaneityFormForm

Acid Test for carbonate mineralsAcid Test for carbonate minerals

A mineral’s physical properties A mineral’s physical properties are controlled by its are controlled by its internal internal

arrangement of atomsarrangement of atoms regularly repeating, orderly patternregularly repeating, orderly pattern

The most common crystalline The most common crystalline structure structure

Silica-oxygen tetrahedronSilica-oxygen tetrahedron – basic – basic building block for silicate mineralsbuilding block for silicate minerals

Minerals can have the same chemical composition Minerals can have the same chemical composition (Carbon) but different physical properties because (Carbon) but different physical properties because

of their crystal structureof their crystal structure

Diamond Diamond GraphiteGraphite

COLORCOLORColor is not usually a definitive property of Color is not usually a definitive property of

a mineral. a mineral. Some minerals have characteristics colorsSome minerals have characteristics colorsOthers vary due to chemical differences or Others vary due to chemical differences or

impurities (atoms mixed inside the main impurities (atoms mixed inside the main elements)elements)

However most minerals have a variety of However most minerals have a variety of colorscolors..

Some Colors of Quartz

STREAKSTREAKFor opaque minerals, if you rub the For opaque minerals, if you rub the

sample across a streak plate, it will leave a sample across a streak plate, it will leave a colored powder. This streak is distinctive colored powder. This streak is distinctive for minerals and is used to identify for minerals and is used to identify minerals. minerals.

Varieties of Hematite – all same color streak

HARDNESS – Mineral’s resistance to HARDNESS – Mineral’s resistance to scratching or abrasion. Minerals with higher scratching or abrasion. Minerals with higher

numbers will scratch minerals belownumbers will scratch minerals below

LUSTER LUSTER

Describes how light reflects off the surface Describes how light reflects off the surface

Categories: Categories: Metallic or Non-metallicMetallic or Non-metallic Metallic – luster of metal – shines like a hard metal Metallic – luster of metal – shines like a hard metal Many non-metallic minerals are SHINY because they Many non-metallic minerals are SHINY because they

are transparent or semi-transparentare transparent or semi-transparent

Non-metallic: Adamantine, vitreous or glassy; silky; pearly; Non-metallic: Adamantine, vitreous or glassy; silky; pearly; greasy; waxy, dull; earthygreasy; waxy, dull; earthy

Examples of metallic lusterExamples of metallic luster

Pyrite (FeS2)Galena (PbS)

More Examples of Metallic Luster

PYRITE

GALENA

Example of non-metallic lusterExample of non-metallic lusterVitreous--quartzVitreous--quartz

Example of non-metallic lusterExample of non-metallic lusterSilky--example plagioclase feldsparSilky--example plagioclase feldspar

Non-metallic and metallic luster – Non-metallic and metallic luster – earthy hematite – metallic hematiteearthy hematite – metallic hematite

Cleavage and FractureCleavage and Fracture

Some minerals split along flat surfaces Some minerals split along flat surfaces (called cleavage planes) when struck (called cleavage planes) when struck hard--this is called mineral cleavage hard--this is called mineral cleavage

Other minerals break unevenly along Other minerals break unevenly along rough or curved surfaces--this is called rough or curved surfaces--this is called fracture fracture

A few minerals have both cleavage and A few minerals have both cleavage and fracture ( mica )fracture ( mica )

FLUORITE

HALITE

Halite (NaCl)Fluorite (CaF2)

Cleavage – due to weak bonds in the crystal structure

Cleavage

BIOTITEMUSCOVITE

Rose Quartz – Conchoidal FractureRose Quartz – Conchoidal Fracture

Conchoidal Fracture - Quartz

Obsidian

NONSILICATE MINERALSCARBONATES

Carbonate ion (CO32-) is prominent in minerals.

Bonds generally weak.Minerals are soft (3-4).Minerals are soluble in acidic water.

Leads to cave development.

Calcite (CaCO3) if transparent canBreak light into 2 images (double refraction)

CALCITE

Acid Test for CarbonatesAcid Test for Carbonates Special Characteristics:Special Characteristics:

Carbonates react with dilute HCl and other Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing acids by fizzing or bubbling (releasing CO2 gas)CO2 gas)

Less than a dozen are common in Less than a dozen are common in most rocksmost rocks

QuartzQuartz Feldspar (group)Feldspar (group) Muscovite (silver white mica)Muscovite (silver white mica) Biotite (black mica)Biotite (black mica) CalciteCalcite PyroxenePyroxene OlivineOlivine Amphibole (group)Amphibole (group) Magnetite, limonite, and other iron oxidesMagnetite, limonite, and other iron oxides PyritePyrite