naturally occurring - materials synthesized in laboratory do not count, must be formed by natural processes in wild
inorganic - not formed by organic chemistry (e.g., sugars, etc.)
homogeneous solid - single substance in solid phase which cannot be physically separated into simpler compounds
definite chemical composition - composition can be represented as chemical formula (e.g., NaCl), although variation in exact composition is possible (e.g., (Mg, Fe)2SiO4 ) [range in color, hardness, specific gravity]
ordered atomic arrangement – repeating structure at the atomic level, which expresses as symmetry in large specimens, i.e., crystalline structure.
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MineralMineral - A naturally occurring, inorganic, - A naturally occurring, inorganic, homogeneous solid with a definite chemical composition homogeneous solid with a definite chemical composition and an ordered atomic arrangement. and an ordered atomic arrangement.
Mineral Properties
Crystal Form• Cleavage/Fracture• Color• Streak Color• Luster
Crystal Form• Cleavage/Fracture• Color• Streak Color• Luster
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
Crystal symmetry is controlled by the Crystal symmetry is controlled by the atomic structure of mineralatomic structure of mineral
Mineral Properties
• Crystal Form• Cleavage/Fracture
Color• Streak Color• Luster
• Crystal Form• Cleavage/Fracture
Color• Streak Color• Luster
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
Characteristic for some minerals, useless for most
QuartzQuartzSiO2
Hardness = 7
Rose QuartzRose QuartzRose QuartzRose Quartz
SmokeySmokeyQuartzQuartz
QuartzQuartzCitrineCitrine
AmethystAmethystAmethystAmethyst
CarnelianCarnelian
OnyxOnyxJasperJasper
Mineral Properties
• Crystal Form• Cleavage/Fracture• Color
Streak Color• Luster
• Crystal Form• Cleavage/Fracture• Color
Streak Color• Luster
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
Streak Color Streak Color - - Color of powdered mineral, which may or may not be the color of the crystal
hematite streak colorhematite streak color
• Crystal Form• Cleavage/Fracture• Color• Streak• Luster
• Crystal Form• Cleavage/Fracture• Color• Streak• Luster
• Hardness• Tenacity
Specific Gravity• Acid Test• Magnetism
• Hardness• Tenacity
Specific Gravity• Acid Test• Magnetism
Specific GravitySpecific Gravity - density of the material (g/cm3)
Mineral Properties
Specific GravitySpecific Gravity
Related to both the atomic weight of the contained the atomic weight of the contained elementselements, and how tightly the atoms are packed
Orthorhombic CarbonatesOrthorhombic CarbonatesAll minerals have same structure, only cation differs
Mineral Formula Cation g/cm3
Aragonite CaCO3 20 2.95
Strontianite SrCO3 38 3.76
Witherite BaCO3 56 4.29
Cerrusite PbCO3 82 6.55
See Page 82 in Lab Manual for Specific Gravities of some
minerals
Mineral Properties
• Crystal Form• Cleavage/Fracture• Color• Streak Color
Luster
• Crystal Form• Cleavage/Fracture• Color• Streak Color
Luster
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
Luster - quality of light reflected from mineral surface
LusterLuster - quality of light reflected from mineral surface- quality of light reflected from mineral surface
metallicmetallicpyrite
goldgold
silversilver
LusterLuster quality of light reflected from mineral surfacequality of light reflected from mineral surface
resinouspearly
vitreous (glassy)non-metallicnon-metallicSome minerals may be listed in Some minerals may be listed in both metallic and non-metallic, or both metallic and non-metallic, or in the incorrect table, i.e., limonitein the incorrect table, i.e., limonite
Mineral Properties
• Crystal Form• Cleavage/Fracture• Color• Streak Color• Luster
• Crystal Form• Cleavage/Fracture• Color• Streak Color• Luster
Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
Hardness - resistance of mineral to scratching or abrasion
Mohs Hardness ScaleMohs Hardness ScaleAustrian mineralogist F. Mohs, 1824
Based on relative hardness of 10 common minerals
Based on relative hardness of 10 common mineralshardhard
softsoft
10. Diamond C9. Corundum Al2O3
8. Topaz Al2SiO4(F,OH)2
7. Quartz SiO2
6. Orthoclase KAlSi3O8
5. Apatite Ca5(PO4)3(F,Cl,OH)4. Fluorite CaF2
3. Calcite CaCO3
2. Gypsum CaSO4
1. Talc Mg3Si4O10(OH)2
Higher numbered minerals scratch lower numbered minerals
fingernailcopper penny
glass plate
Fig. 02.14
Muscovite
Hardness < 2
Can scratch with fingernail (H=2.5)
Muscovite
Hardness < 2
Can scratch with fingernail (H=2.5)
Fig. 02.15c
Fluorite
Hardness =4
Can scratch copper penny (H=3.5), but not glass plate (H=5.5)
Fluorite
Hardness =4
Can scratch copper penny (H=3.5), but not glass plate (H=5.5)
Fig. 02.15a
Quartz
Hardness =7
Scratches glass plate (H=5.5). Hardest of common minerals
Quartz
Hardness =7
Scratches glass plate (H=5.5). Hardest of common minerals
Mineral Properties
• Crystal Form• Cleavage/Fracture• Color• Streak• Luster
• Crystal Form• Cleavage/Fracture• Color• Streak• Luster
• Hardness• Tenacity• Specific Gravity
Acid TestAcid Test• Magnetism
• Hardness• Tenacity• Specific Gravity
Acid TestAcid Test• Magnetism
Reaction to dilute acid; especially useful in identifying carbonate minerals
Minerals like calcite react with weak acid, dissolving the Minerals like calcite react with weak acid, dissolving the mineral and producing lots of bubbles (effervescence)mineral and producing lots of bubbles (effervescence)
Calcite: CaCO3
HCl + CaCO3 > H2O + Cl- + Ca+ + CO2
Dolomite: CaMg(CO3)2
Mineral Properties
• Crystal Form• Cleavage/Fracture• Color• Streak• Luster
• Crystal Form• Cleavage/Fracture• Color• Streak• Luster
• Hardness• Tenacity• Specific Gravity• Acid Test
Magnetism
• Hardness• Tenacity• Specific Gravity• Acid Test
Magnetism
Some minerals strongly attract magnets. Characteristic of magnetite and some other iron minerals
Mineral Properties
• Crystal Form
Cleavage/Fracture• Color• Streak Color• Luster
• Crystal Form
Cleavage/Fracture• Color• Streak Color• Luster
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
FractureFracture - any breakage that is not cleavage
conchoidalconchoidalfracturefracture
Characteristic of quartz, chert and flint
Fig. 02.23
conchoidal fracture
Mineral Properties
• Crystal Form
Cleavage/Fracture• Color• Streak Color• Luster
• Crystal Form
Cleavage/Fracture• Color• Streak Color• Luster
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
• Hardness• Tenacity• Specific Gravity• Acid Test• Magnetism
CleavageCleavage - tendency to split along planes of weakness corresponding to weaker chemical links in internal structure of crystal
A single crystal can display several cleavage directions.
The cleavage directions are not always at right angles to each other. They The cleavage directions are not always at right angles to each other. They also are not necessarily parallel to the crystal faces of the mineral.also are not necessarily parallel to the crystal faces of the mineral.
1 direction 2 directions
Fig. 02.19a
One Direction of Cleavage
One Direction of Cleavage
Two Directions of CleavageTwo Directions of Cleavage
Cleavage DirectionCleavage Direction
Each set of parallel planes of weakness is one direction
Three Directions of Cleavage
Fig. 02.22http://www.geology.sdsu.edu/visualgeology
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Fluorite Crystals
Four Directions of Cleavage
Six directions of Cleavage: Sphalerite (ZnS)