9/14/15 The eight most important What is a mineral? Rock Forming Minerals • Quartz • Olivine • Orthoclase feldspar • Augite • Plagioclase feldspar • Hornblende • Muscovite mica • Biotite mica • (Felsic minerals) • (Mafic minerals) The main way we can distinguish How can we identify minerals? minerals is by their physical properties. Hardness-resistance to scratching" Luster- how a mineral reflects light Mohs Hardness Scale • 1. Talc • Other implements to • Metallic-looks • Nonmetallic • 2. Gypsum use for hardness. “metallic” – Adamantine=brilliant • 3.Calcite • Fingernail 2.5 – Vitreous=glassy • 4. Fluorite – Resinous=like resin • 5. Apatite • Penny 3.5 • Submetallic-looks – Waxy=like wax • 6. Orthoclase Feldspar • Glass plate 5.5 slightly metallic – Pearly=like a pearl • 7. Quartz • Nail or knife 5.5 • 8. Topaz – Silky=parallel fibers • 9. Corundum – Earthy=dull • 10. Diamond 1 9/14/15 Metallic luster Submetallic luster • Reflects light like a • Looks slightly metallic metal – magnetite – Galena, Copper, – pyrite Nonmetallic luster Nonmetallic luster • Vitreous luster • Waxy luster-looks like – Glassy look wax – Quartz – Serpentine Nonmetallic luster Nonmetallic luster • Pearly luster-like a • Silky-parallel fiber pearl – Gypsum-satin spar – Gypsum 2 9/14/15 Nonmetallic luster Diaphaneity • Transparent- can see • Dull- earthy through it • Little reflection • Translucent- lets light – limonite through but you can’t see image • Opaque- doesn’t let light through Color Color • Some minerals it is • Some minerals occur very distinctive in many colors • Sulfur- always yellow Color Streak • Quartz- color variable – Smoky-black – Rock crystal- colorless • Color of the mineral – Amethyst-purple on a porcelain tile – Rose-pink – Pyrite-black – Milky- white – Hematite- red brown – Citrine-yellow brown 3 9/14/15 Specific gravity Crystal shape • The ratio of the mass • Water- 1.0 • Based on crystal • Isometric of a substance to an • Graphite-2.2 symmetry • Tetragonal equal volume of water • Quartz-2.65 • 6 crystal classes • Hexagonal • Pyrite-5.0 • Monoclinic • Galena-7.5 • Orthorhombic • Gold-19.3 • Triclinic Fracture- non-planar breakage Cleavage • Tendency of a mineral • 1-direction to break along planes • 2-direction =90 • Conchoidal fracture determined by the • 2 direction not = 90 – Quartz internal atomic arrangement • 3 direction=90 • 3 direction not = 90 • 4 directions • 6 directions Cleavage Cleavage • 1 direction- basal • 2 directions at 90 cleavage • Orthoclase feldspar • Muscovite mica 4 9/14/15 Cleavage Cleavage • 2 directions not at 90 • 3 directions at 90 • Hornblende • Cubic cleavage • Halite Cleavage Cleavage • 3 directions not at 90 • 4 directions • Rhombic cleavage • Octahedral cleavage • Calcite • Fluorite Other properties" Cleavage • Double refraction • Magnetism- magnetite • 6 directions • Feel- talc-greasy • Dodecahedral • Odor-sulfur cleavage • Taste- halite • Sphalerite • Reaction with Hydrochloric acid • Fluorescence 5 9/14/15 The properties of minerals " • Color variable are very distinctive and • Vitreous luster determine how the mineral can be • Hardness 7 used • Hexagonal crystals • Conchoidal fracture • S.G. 2.7 • Used for making glass, clocks, silicon metal for computer chips Orthoclase Feldspar" Muscovite mica" KAlSi30 8 KAl3Si3O10(OH)2 • Colorless to gray • Pink to White • Vitreous luster • 2 directions of • H 2-2.5 Cleavage at 90 • 1 direction of • H 6 Cleavage • Used for making • Used in toothpaste, porcelain and as a cosmetics, lamp mild abrasive shades. Plagioclase Feldspar" Plagioclase Feldspar" NaAlSi308-CaAl2Si208" NaAlSi308-CaAl2Si208" • White to Dark Gray • White to Dark Gray sometimes Blue gray sometimes Blue gray • Vitreous luster • Vitreous luster • H-6 • H-6 • 2 directions of cleavage at • 2 directions of 90 cleavage at 90 • Striations • Striations • Called Labradorite • Used for making • Used for ceramics and porcelain, ceramics building stone 6 9/14/15 Biotite mica" Augite" K(MgFe)3Al3Si3O10(OH)2 Ca(Mg,Fe,Al)(Al,Si)06 • Dark green to black • Color- Dark green • Vitreous luster • Vitreous Luster • H 2-2.5 • Hardness 6 • 1 direction of cleavage • 2 directions of Cleavage at about 90 Hornblende" Olivine" (Na,Ca)2-3(Mg,Fe,Al)5Si6(Si,Al)2O22(OH)2 (Fe,Mg)2SiO4 • Black to Dark Green • Olive green • Vitreous luster • Vitreous luster • Hardness- 6 • Hardness-6.5 • 2 directions of • Conchoidal fracture cleavage not at 90 • SG-3.4 • SG 3.4 • Used as gemstone (Peridot) Copper " Sulfur" Cu S • Yellow color • Metallic luster • Vitreous-resinous luster • Hardness 3.5 • Distinctive odor • Cleavage –none • Used for matches, • Color –copper red fertilizers, drugs. • Streak- copper red • Used for wire, pennies 7 9/14/15 Graphite" Halite" C NaCl • Dark gray to black • Colorless to white • Dull to metallic • Dull to vitreous luster • Hardness 1-2 • Hardness about 2 • Low Specific Gravity • Cleavage 3=90(cubic) • Used for pencil lead, • Used for food dry lubricants, flavoring and electrodes, fishing preservation, salting poles, tennis rackets. roads. Fluorite" Hematite" CaF2 Fe203 • Color variable • Dull to metallic luster • Vitreous Luster • Color gray to red • Hardness 4 brown • 4 directions of • Hardness 1-6 cleavage (octahedral) • Streak red brown • Used in Toothpaste • Used for making steel and as a pigment Magnetite" Bauxite" Fe304 Al(OH)3 • Dull to Submetallic • Color yellow brown luster • Luster dull • Color-gray to black • Hardness 2-4 • Moderate specific • Composed of circular gravity fragments • Magnetic • Used as an ore of • Used for making steel Aluminum 8 9/14/15 Corundum" Pyrite" Al203 FeS2 • Metallic luster • Dull to vitreous luster • Brassy yellow color • Red brown-blue gray • Streak black • Hardness 9 • H-6-61/2 • Hexagonal crystals • Specific gravity is moderate • Used as a gemstone and abrasive • Used for making sulfuric acid and for collectors Galena" Chalcopyrite" PbS FeCuS2 • Metallic luster • Gray color • Sub-Metallic luster • Hardness 2.5 • Brassy yellow color • Gray Streak • H-4 • Specific gravity very heavy • Moderate specific • Cleavage 3=90(cubic) gravity • Lead ore- weights, • Streak greenish black batteries, x ray shields • Major ore of copper Calcite" Gypsum" CaCO3 CaSO4. 2H2O • Vitreous luster • Dull –vitreous-silky- • Color variable pearly luster • Hardness 3 • Colorless-white • Cleavage 3 not = 90 • (rhombohedral) • Hardness 2 • Reacts with Hydrochloric • Cleavage 3 not=90 acid • Used for sheetrock, • Used for cement, antacids, soil amendment fertilizer and plaster of paris 9 9/14/15 Apatite" Garnet" Ca5(PO4)3(OH,F,Cl) Complex Silicate • Vitreous luster • Vitreous luster • Color variable-brown, • Color variable golden, green, blue • Hardness 7.5 • Hardness 5 • Dodecahedral crystals • Hexagonal crystals • Conchoidal fracture • Used in fertilizers, • Used for gemstone and detergents. abrasive Talc" Topaz" Mg3Si4O10(OH)2 Al2SiO4(F,OH)2 • Dull to vitreous luster • Hardness 1 • Vitreous luster • Color white to light • Color variable green • Hardness 8 • Greasy feel • Basal cleavage • Used for baby powder • Used as a gemstone and cosmetics 10 .