1. Rocks and Minerals I http://www.geology.wisc.edu/~maher/air/air14.htm

2. What distinguishes rocks from minerals? Composition Composition A mineral is homogeneous and has a fixed composition. It is formed through natural processes and is usually inorganic. It has a defined crystal structure. John Veevaert John H. Betts

3. What distinguishes rocks from minerals? Composition Composition A rock is heterogeneous and formed from two or more minerals. Andrew Alden http://www2.vscc.cc.tn.us/svinson/geo100/se dimentary.html

4. Minerals Let’s take a look at some of the characteristics of minerals and their tests. Let’s take a look at some of the characteristics of minerals and their tests. Lou Perloff

5. Mineral Formulas A mineral has a definite chemical formula such as: NaCl, called halite; CuAl 6 (PO 4 ) 4 (OH) 8 ·4(H 2 O), known as turquoise; or (K(Mg,Fe) 3 AlSi 3 O 10 )(OH) 2 ) which is biotite. John Betts

6. Mineral Color Color alone is not the best identifier of a mineral because even small inclusions may change the color you see. These photos are varied forms of quartz. Patrick Laird Floyd Hawk Mike Streeter

7. Mineral Streak The powdered color of a mineral is characteristic. You can see the color by dragging the mineral across a rough surface. The result is called a streak. Patrick Laird http://geology.csupomona.edu/alert/mineral/streak.htm

8. Mineral Luster Mineral luster is a term for describing the way light is reflected from the surface of a mineral. Lusters: metallic shiny dull non-metallic adamantine earthy pearly silky greasy resinous glassy Galena - metallic Spodumene – glassy http://webmineral.com/specimens/picshow.php?id=1091 http://webmineral.com/data/Galena.shtml

9. Mineral Hardness Hardness is a mineral’s resistance to being scratched. A harder mineral will scratch a softer one. Hardness is a relative measure and is assigned a number based on the Mohs Scale. www.yuprocks.com Lou Perloff Diamond hardest Talc softest

10. Mineral Hardness Hardness (Mohs) Mineral Absolute Hardness 1TalcTalc (Mg 3 Si 4 O 10 (OH) 2 )1 2GypsumGypsum (CaSO 4 ·2H 2 O)3 3CalciteCalcite (CaCO 3 )9 4FluoriteFluorite (CaF 2 )21 5 ApatiteApatite (Ca 5 (PO 4 ) 3 (OH-,Cl-,F- )) 48 6 Orthoclase Feldspar Orthoclase Feldspar (KAlSi 3 O 8 ) 72 7QuartzQuartz (SiO 2 )100 8TopazTopaz (Al 2 SiO 4 (OH-,F-) 2 )200 9CorundumCorundum (Al 2 O 3 )400 10DiamondDiamond (C)1500 2.5Fingernail 2.5–3Gold, Silver 3Copper penny 4-4.5Platinum 4-5Iron 5.5Knife blade 6-7Glass 6.5Iron pyrite 7+ Hardened steel file

11. Density or Specific Gravity All minerals have a density. Densities that are high or low may be helpful in identifying the mineral. Density is the amount of matter in a given volume of the substance. D=M/V Specific gravity is the density of a substance compared to the density of water. Because specific gravity is a ratio with no units, it is often used in the place of density. http://www.spaceman.ca/mineral/index.php?ViewImage=110 Galena very dense Gypsum low density

12. Other Mineral Properties http://geology.csupomona.edu/alert/mineral/other.htm http://www.yourgemologist.com/magnetite.html Some carbonate minerals react to an acid such as HCl. The reaction produces carbon dioxide gas which will “fizz” on the mineral surface. Some minerals show magnetism or are attracted to magnets. Magnetite is the best example and has been used to make magnets.

13. Identifying a Mineral When geologists or gemologists identify a mineral they use several properties. The properties they select depend on the sample itself and what they suspect the substance is. http://www.minerals.si.edu/images/gallery/mineral.htm