Transcript
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
top related