modul 5b - minerals, identification
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Minerals: identification
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Identification of Minerals
QuestionsQuestions
How can you identify minerals?How can you identify minerals?
How do geologists identify minerals?How do geologists identify minerals?
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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
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Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
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
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Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
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
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3. Streak3. Streak
The color of a mineral in powder formThe color of a mineral in powder form
Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
Figure 1.8Figure 1.8
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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
Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
Have a metallic luster Have a metallic luster
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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
Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
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Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
Various Types of CleavageVarious Types of Cleavage
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Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
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
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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
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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
Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
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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
Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
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Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
M o h s H a r d n e s s
S c a l e
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Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
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==
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Identifying Physical Properties of MineralsIdentifying Physical Properties of Minerals
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