Modul 5b - Minerals, Identification

7/28/2019 Modul 5b - Minerals, Identification

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Minerals: identification



Identification of Minerals

QuestionsQuestions

How can you identify minerals?How can you identify minerals?

How do geologists identify minerals?How do geologists identify minerals?



Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals

1.1. Crystal formCrystal form2.2. Color Color

3.3. StreakStreak

4.4. Luster Luster 5.5. CleavageCleavage

6.6. FractureFracture

7.7. HardnessHardness

8.8. TenacityTenacity

9.9. Specific gravitySpecific gravity

10.10. TasteTaste

11.11. MagnetismMagnetism12.12. Reaction with acidReaction with acid

13.13. StriationsStriations




1. Crystal form1. Crystal form

Is a set of crystalline faces having a definiteIs a set of crystalline faces having a definitegeometric relationship to one another geometric relationship to one another

GarnetGarnet

QuartzQuartz




Colors of ruby and sapphire,Colors of ruby and sapphire,varieties of corundum (Alvarieties of corundum (Al22OO33)

2. Color 2. Color Is due to visible wavelengths of light not absorbedIs due to visible wavelengths of light not absorbed

Is the most obvious but least reliable property to useIs the most obvious but least reliable property to use

for identificationfor identification

Smoky quartz

Milky quartz

Amethyst

Citrine

) Colors of Varieties of QuartzColors of Varieties of Quartz



3. Streak3. Streak

The color of a mineral in powder formThe color of a mineral in powder form


Figure 1.8Figure 1.8



4.4. Luster Luster

Is the intensity of light reflected from a surfaceIs the intensity of light reflected from a surface

Has a nonmetallic luster Has a nonmetallic luster

Pyrite

Galena

Potassium feldspar


Have a metallic luster Have a metallic luster



5. Cleavage5. Cleavage

Is breakage along planes of weaknessIs breakage along planes of weakness Is due to weak bonding between those planesIs due to weak bonding between those planes





Various Types of CleavageVarious Types of Cleavage




Pyramidal Cleavage Cubic Cleavage, and Rhombohedral CleavagePyramidal Cleavage Cubic Cleavage, and Rhombohedral Cleavage

Displayed by Fluorite, Halite, and CalciteDisplayed by Fluorite, Halite, and Calcite

FluoriteFluoriteHaliteHalite

CalciteCalcite



Identifying Physical Properties of MineralsIdentifying Physical Properties of MineralsDistinguishing between Cleavage Planes and Crystal FacesDistinguishing between Cleavage Planes and Crystal Faces

••Cleavage Planes:Cleavage Planes:

Repeated like a seriesRepeated like a series

of step or terracesof step or terraces

•• A A crytalcrytal face:face:

A single surface A single surfaceNo repetitions of theNo repetitions of the

crystal face withincrystal face within

a crystala crystal



6. Fracture6. Fracture

Is breakage in random directionsIs breakage in random directions Is due to the absence of weak bonding between planesIs due to the absence of weak bonding between planes

Conchoidal fracture yields scalloped edges like in broken glassConchoidal fracture yields scalloped edges like in broken glass




7. Hardness7. Hardness

Is the resistance to scratchingIs the resistance to scratching Is based on the MohIs based on the Moh’’s Scales Scale

1 talc1 talc

2 gypsum2 gypsum 3 calcite3 calcite

4 fluorite4 fluorite

5 apatite5 apatite 6 potassium feldspar (orthoclase)6 potassium feldspar (orthoclase)

7 quartz7 quartz

8 topaz8 topaz

9 corundum9 corundum

10 diamond10 diamond





M o h s H a r d n e s s

S c a l e




8. Tenacity8. Tenacity

resistance to breaking or bendingresistance to breaking or bending

9. Specific gravity: an expression of heaviness9. Specific gravity: an expression of heaviness

density of a substancedensity of a substance XX g/cmg/cm33

density of water 1 g/cmdensity of water 1 g/cm33

10. Taste10. Taste

Halite (rock salt) tastes saltyHalite (rock salt) tastes salty

11. Magnetism11. Magnetism magnetite attracts a magnetmagnetite attracts a magnet

SGSG == == XX==




12. Reaction with acid12. Reaction with acid

minerals containing a COminerals containing a CO33 ion fizz (release COion fizz (release CO22) when) when

in contact with hydrochloric acidin contact with hydrochloric acid

2HCl + CaCO2HCl + CaCO33

→→ CaCa2+2+ + 2Cl+ 2Cl-- + H+ H22

O + COO + CO22

13. Reaction with acid Striations13. Reaction with acid Striations

Are sawAre saw--tooth lines present on crystal planes due totooth lines present on crystal planes due tolamellar twinning (repetition) of crystals on that planelamellar twinning (repetition) of crystals on that plane

Striations are characteristic of plagioclase feldspar,Striations are characteristic of plagioclase feldspar,

calcite, dolomite, galena, and sphaleritecalcite, dolomite, galena, and sphalerite

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Modul 5b - Minerals, Identification