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Download Color of a mineral in its powdered form
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1 How are minerals identified? Physical properties Crystal Form • External expression of the crystal structure • Crystal growth is often interrupted because of competition for space and rapid loss of heat 2 The mineral garnet often exhibits good crystal form 3 Quartz in Granite Luster Galena is a lead sulfide that Copper (Cu) Quartz (SiO2) 4 5 6 7 8 displays _________ luster Color Generally unreliable for mineral identification Different minerals can have the same color 9 10 Quartz (SiO2) exhibits a variety of colors Streak Color of a mineral in its powdered form 11 12 ¢ Helpful in distinguishing different forms of the same mineral Hematite Hardness • Resistance of a mineral to abrasion or scratching 13 Hardness • Resistance of a mineral to abrasion or scratching • Depends on the bonds in the crystal structure 14 Hardness • Resistance of a mineral to abrasion or scratching • Depends on the bonds in the crystal structure 1 • All minerals are compared to a standard scale: the Mohs scale of hardness 15 16 17 Cleavage Tendency to break along planes of weak bonding Produces flat, shiny surfaces Described by resulting geometric shapes -Number of planes -Angles between adjacent planes 18 Three examples of perfect cleavage – fluorite, halite, and calcite 19 20 Cleavage Galena (PbS) 21 Muscovite (mica) cleavage 22 Fracture Absence of cleavage when a mineral is broken- all bonds are equally strong (weak) 23 Fracture - Olivine 24 Specific Gravity Ratio of the weight of a mineral to the weight of an equal volume of water Average Earth crust value is approximately 2.7 g/cm3 25 Other properties Magnetism Reaction to hydrochloric acid Double refraction Taste Smell Radioactivity 26 USES OF MINERALS “ If you can’t grow it, you have to mine it!” 2 27 USES OF MINERALS Jewelry USDA daily food requirements Graphite in pencils Metals (all originate from mining minerals) Clays Cement Energy, etc., etc., etc. 28 USES OF MINERALS Visit the NDGS Minerals web site at: www.ndsu.edu/nd_geology 3
