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) 2 SiO 4 ) [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. Mineral - A naturally occurring, inorganic, homogeneous solid with a definite chemical composition 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 atomic 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

Quartz SiO 2 Hardness = 7 Rose Quartz SmokeyQuartz Quartz Citrine AmethystAmethyst Carnelian Onyx Jasper

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 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 Gravity Specific Gravity - density of the material (g/cm 3 ) Mineral Properties

Specific Gravity the atomic weight of the contained elements Related to both the atomic weight of the contained elements, and how tightly the atoms are packed Orthorhombic Carbonates All minerals have same structure, only cation differs MineralFormulaCation g/cm3 AragoniteCaCO StrontianiteSrCO WitheriteBaCO CerrusitePbCO 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

Luster - quality of light reflected from mineral surface metallic pyrite gold silver

Luster quality of light reflected from mineral surface resinous pearly vitreous (glassy) non-metallic Some minerals may be listed in both metallic and non-metallic, or in 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 Scale Austrian mineralogist F. Mohs, 1824 Based on relative hardness of 10 common minerals hard soft 10. Diamond C 9. Corundum Al 2 O 3 8. Topaz Al 2 SiO 4 (F,OH) 2 7. Quartz SiO 2 6. Orthoclase KAlSi 3 O 8 5. Apatite Ca 5 (PO 4 ) 3 (F,Cl,OH) 4. Fluorite CaF 2 3. Calcite CaCO 3 2. Gypsum CaSO 4 1. Talc Mg 3 Si 4 O 10 (OH) 2 Higher numbered minerals scratch lower numbered minerals fingernail copper penny glass plate

Fig Muscovite Hardness < 2 Can scratch with fingernail (H=2.5) Muscovite Hardness < 2 Can scratch with fingernail (H=2.5)

Fig c 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 a 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 Test Magnetism Hardness Tenacity Specific Gravity Acid Test Magnetism Reaction to dilute acid; especially useful in identifying carbonate minerals

Minerals like calcite react with weak acid, dissolving the mineral and producing lots of bubbles (effervescence) Calcite: CaCO 3 HCl + CaCO 3 > H 2 O + Cl - + Ca + + CO 2 Dolomite: CaMg(CO 3 ) 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 Fracture - any breakage that is not cleavage

conchoidalfracture Characteristic of quartz, chert and flint

Fig 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 Cleavage - 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 also are not necessarily parallel to the crystal faces of the mineral. 1 direction2 directions

Fig a One Direction of Cleavage

Two Directions of Cleavage Cleavage Direction Each set of parallel planes of weakness is one direction

Three Directions of Cleavage

Fig

Fluorite Crystals Four Directions of Cleavage Six directions of Cleavage: Sphalerite (ZnS)