mineralogy, geology

1. MINERALOGYMINERALOGY
 Branch of Geology that deals with theBranch of Geology that deals with the
study of Mineralsstudy of Minerals
 The Solid crust of the earth is made up ofThe Solid crust of the earth is made up of
rocks. Rocks are aggregates of mineralsrocks. Rocks are aggregates of minerals
 The property of a rock is in turn based onThe 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.

3. Atoms combine to formAtoms combine to form
ElementsElements
 ElementsElements – fundamental component that– fundamental component that
can not be broken down into othercan not be broken down into other
substances by ordinary chemicalsubstances by ordinary chemical
processesprocesses
 Elements combine to form mineralsElements combine to form minerals

4. General Facts About MineralsGeneral Facts About Minerals
5,000 + minerals have been identified5,000 + minerals have been identified
 A few are “native elements” -- made ofA 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 theMost 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.

5. Gold (Au)
Silver (Ag)
Platinum (Pt)
Diamond (C)
Graphite (C)
Sulfur (S)
Copper (Cu)
MINERALS
NATIVE ELEMENTS
Copper
Silver
Gold

6. Mineral CriteriaMineral Criteria
1. Naturally occurring – not manufactured1. Naturally occurring – not manufactured
2.Are Solids2.Are Solids
3.Inorganic – minerals not made by living things3.Inorganic – minerals not made by living things
(organic)(organic)
4.Crystalline solid – atoms have specific4.Crystalline solid – atoms have specific
arrangement or crystal structurearrangement or crystal structure
5.5. Have a definite chemical composition – mayHave a definite chemical composition – may
be a single element or combinationbe a single element or combination

8. MINERAL FORMATIONMINERAL FORMATION
 CRYSTALLIZE FROM MAGMA or LAVACRYSTALLIZE FROM MAGMA or LAVA
solidification of liquid magma/lava to solidsolidification of liquid magma/lava to solid
with a definite internal arrangement ofwith 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 solutiondissolved minerals come out of solution
(water) to form solids(water) to form solids

9. Minerals are identified by theirMinerals are identified by their
Physical PropertiesPhysical Properties
ColorColor
StreakStreak
Luster – metallic, non-metallicLuster – metallic, non-metallic
Hardness – Mohs Hardness Scale (1-10)Hardness – Mohs Hardness Scale (1-10)
CleavageCleavage
FractureFracture
Crystal Form – determines physical propertiesCrystal Form – determines physical properties
TenacityTenacity
DiaphaneityDiaphaneity
FormForm

11. A mineral’s physical propertiesA mineral’s physical properties
are controlled by itsare controlled by its internalinternal
arrangement of atomsarrangement of atoms
regularly repeating, orderly patternregularly repeating, orderly pattern

12. The most common crystallineThe most common crystalline
structurestructure
 Silica-oxygen tetrahedronSilica-oxygen tetrahedron – basic– basic
building block for silicate mineralsbuilding block for silicate minerals

13. Minerals can have the same chemical compositionMinerals 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
DiamondDiamond GraphiteGraphite

16. COLORCOLOR
 Color is not usually a definitive property ofColor is not usually a definitive property of
a mineral.a mineral.
 Some minerals have characteristics colorsSome minerals have characteristics colors
 Others vary due to chemical differences orOthers vary due to chemical differences or
impurities (atoms mixed inside the mainimpurities (atoms mixed inside the main
elements)elements)
 However most minerals have a variety ofHowever most minerals have a variety of
colorscolors..

17. Some Colors of Quartz

19. STREAKSTREAK
 For opaque minerals, if you rub theFor opaque minerals, if you rub the
sample across a streak plate, it will leavesample across a streak plate, it will leave
a colored powder. This streak isa colored powder. This streak is
distinctive for minerals and is used todistinctive for minerals and is used to
identify minerals.identify minerals.

20. Varieties of Hematite – all same color streak

22. HARDNESS – Mineral’s resistance toHARDNESS – Mineral’s resistance to
scratching or abrasion. Minerals with higherscratching or abrasion. Minerals with higher
numbers will scratch minerals belownumbers will scratch minerals below

23. LUSTERLUSTER
 Describes how light reflects off the surfaceDescribes how light reflects off the surface
 Categories:Categories: Metallic or Non-metallicMetallic or Non-metallic
Metallic – luster of metal – shines like a hard metalMetallic – luster of metal – shines like a hard metal
Many non-metallic minerals are SHINY because theyMany 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

24. Examples of metallic lusterExamples of metallic luster

25. Pyrite (FeS2)
Galena (PbS)
More Examples of Metallic Luster
PYRITE
GALENA

26. Example of non-metallic lusterExample of non-metallic luster
 Vitreous--quartzVitreous--quartz

27. Example of non-metallic lusterExample of non-metallic luster
 Silky--example plagioclase feldsparSilky--example plagioclase feldspar

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

30. Cleavage and FractureCleavage and Fracture
 Some minerals split along flat surfacesSome minerals split along flat surfaces
(called cleavage planes) when struck(called cleavage planes) when struck
hard--this is called mineral cleavagehard--this is called mineral cleavage
 Other minerals break unevenly alongOther minerals break unevenly along
rough or curved surfaces--this is calledrough or curved surfaces--this is called
fracturefracture
 A few minerals have both cleavage andA few minerals have both cleavage and
fracture ( mica )fracture ( mica )

32. FLUORITE
HALITE
Halite (NaCl)
Fluorite (CaF2)
Cleavage – due to weak bonds in
the crystal structure

34. Cleavage
BIOTITE
MUSCOVITE

35. Rose Quartz – Conchoidal FractureRose Quartz – Conchoidal Fracture

36. Conchoidal Fracture - Quartz
Obsidian

38. NONSILICATE MINERALS
CARBONATES
Carbonate ion (CO3
2-
) 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 can
Break light into 2 images
(double refraction)
CALCITE

40. Acid Test for CarbonatesAcid Test for Carbonates
 Special Characteristics:Special Characteristics:
Carbonates react with dilute HCl and otherCarbonates react with dilute HCl and other
acids by fizzing or bubbling (releasingacids by fizzing or bubbling (releasing
CO2 gas)CO2 gas)

41. Less than a dozen are common inLess 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