2. Physical Properties Quartz Crystal Shape Hexagonal Luster Nonmetallic (Vitreous) Color Clear to Milky Streak No Streak Hardness H = 7 Cleavage No Cleavage Fracture Conchoidal Specific Gravity S.P. = 2.65
3. Crystal Shape Crystal form(or shape) is the outward expression of a mineral’s orderly internal arrangement of atoms. The cubic shape of halite (salt) crystals results from the regular arrangement of sodium and chlorine atoms forming the crystal.
4. Luster Luster is the way light is reflected from the surface of the mineral. It is the way a mineral shines or doesn’t shine. Minerals can have metallic or non-metallic luster. Hematite occurs in both metallic and non-metallic varieties .
5. Color Color, the wavelength of light reflected from the mineral’s surface, is not always an effective property for identifying minerals. Sulfur is always yellow so its color is always a distinguishing property. Quartz occurs in many colors as seen in the pictures above, so you must use other properties to identify it.
6. Streak Streak is color of the mineral in powder form. It is tested by rubbing a metallic mineral across a piece of unglazed porcelain called a streak plate. Hematite (Fe 2 O 3 ) has a reddish-brown streak whether the sample is metallic or non-metallic in appearance.
7. Hardness Hardness is a mineral’s ability to resist abrasion or scratching. One mineral (or common object) of known hardness is scratched against another mineral, the harder mineral will leave a scratch in the softer mineral. The Moh’s Hardness Scale arranges common minerals by relative hardness.
8. Cleavage Cleavage is when a mineral breaks into flat surfaces along planes of weak bonding in the crystal structure. Fluorite (CaF 2 ), an octahedral crystal, breaks along four cleavage planes.
9. Fracture Fracture is the way a mineral breaks when it doesn’t break along cleavage planes. Quartz has conchoidal fracture. Asbestos has splintery or fibrous fracture.
10. Specific Gravity Specific Gravity is the weight of a mineral compared to the weight of an equal volume of water. Potassium Feldspar (KAl 2 Si 3 O 8 ) has a specific gravity of 2.65 and Galena (PbS) has a a specific gravity of 7.6.
11. Native Elements Native elements are minerals composed of only one element. Sulfur (S) Diamond (C) Graphite (C) Gold(Au) Silver (Ag) Copper (Cu) Platinum (Pt)
12. Ten Most Abundant Elements in the Earth’s Crust O Oxygen Si Silicon Al Aluminum Fe Iron Ca Calcium Na Sodium K Potassium Mg Magnesium Ti Titanium H Hydrogen Potassium Feldspar (KAl 2 Si 3 O 8 ) Augite (Ca,Na,Mg,Fe +2 ,Fe +3 , Al,Ti) 2 {(Si,Al) 2 O 6 } Muscovite K 2 Al 4 [Si 6 Al 2 O 20 ](OH,F) 4 Limonite FeO(H 2 O) 2
13. Silicate Minerals Silicate minerals are composed of Silicon (Si 4+ ) and Oxygen (O 2- ) plus some positively charged metal ions. Quartz (SiO 2 ) Potassium Feldspar (KAl 2 Si 3 O 8 )
14. Silica Tetrahedron The Silica Tetrahedron is the basic building-block of silicate minerals. It is composed of one silicon ion (Si 4+ ) surrounded by four oxygen ions (O 2- ). Silica Tetrahedrons link up in various patterns and bond with metal ions to form specific silicate minerals.
15. In Olivine, all the Fe 2+ ions (green) above can be replaced by Mg 2+ ions (red) in any proportion without changing the structure of the mineral in any significant way. Olivine ([Fe,Mg] 2 SiO 4 )
20. Carbonate Minerals Carbonate minerals are composed of positively charged metal ions joined with carbonate (CO 3 2- ) ions. Calcite CaCO 3 Dolomite (Mg,Ca)CO 3
21. Oxide Minerals Oxide minerals are composed of positively charged metal ions joined with oxygen (O 2- ) ions. Limonite FeO(H 2 O) 2 Magnetite Fe 2 O 3 Corundum Al 2 O 3
22. Sulfide Minerals Sulfide minerals are composed of positively charged metal ions joined with sulfide (S 2- ) ions. Pyrite FeS 2 Galena PbS Sphalerite ZnS Chalcopyrite (Cu,Fe)S 2 Argentite Ag 2 S
23. Phosphate Minerals Phosphate minerals are composed of positively charged metal ions joined with phosphate (PO 4 3- ) ions. Turquois Apatite CuAl 6 (PO 4 ) 4 (OH) 8 . 4H 2 O Ca 5 F(PO 4 ) 3 (OH,F,Cl)
