EARTH MATERIALS Minerals, Rocks, and Mineral Resources
MINERALS • Naturally occurring • Inorganic • Crystalline solid • Definite chemical composition
ARE THESE MINERALS? WHY OR WHY NOT? • Diamond • Coal • Wood • Quartz • Graphite
WHAT IS CRYSTALLINE? • The atoms have a specific arrangement called the crystal structure • Every mineral has its own distinctive crystal structure
CRYSTAL STRUCTURE • The ordered pattern of atoms in the mineral. • Hexagonal • Cubic • Horizontal (thin, flexible sheets)
MINERAL FORMATION • Atoms organize to form crystalline solids • Recrystallization of atoms from solids and liquids in rock-forming environments
MINERAL IDENTIFICATION • The arrangement and type of atoms gives every mineral a set of physical and chemical properties that can be used to identify the mineral.
1. COLOR • Many minerals have a characteristic color • Some colors may be caused by impurities • Many minerals come in more than 1 color (variable color).
2. LUSTER • The way a mineral looks in reflected light • Metallic—shines like a metal • Nonmetallic—may be shiny, but does not shine like a metal • Glassy, waxy, pearly, earthy (dull)
3. STREAK • The color of the powdered form of the mineral • Test performed using an unglazed, porcelain streak plate • The streak color is not always the same color as the mineral
4. HARDNESS • Moh’s Scale of Hardness • To test for hardness, scratch the unknown mineral with an object of known hardness. • Objects include glass plate, penny, fingernail.
MOH’S SCALE OF HARDNESS • Ranges from 1 to 10. • 1 is the softest, 10 is the hardest.
1. Talc • 2. Gypsum 2.5 Fingernail • 3. Calcite 3.5 Copper Penny • 4. Fluorite 4.5 Iron Nail • 5. Apatite 5.5 Glass Plate • 6. Feldspar • 7. Quartz 7.5 Streak Plate • 8. Topaz • 9. Corundum • 10. Diamond
FRACTURE • A mineral breaks producing an uneven breaking surface. • Does NOT follow the atomic arrangement. • Irregular, Fibrous, Curved (conchoidal)
CLEAVAGE • The ability of a mineral to break along zones of weakness. • Forms smooth to semi-smooth parallel sides or surfaces. • The break will follow the atomic arrangement. Predictable pattern!
DENSITY • Every mineral has its own specific density. • May be called specific gravity—density compared to water.
OTHER PROPERTIES • Chemical reaction with HCl—Hydrochloric Acid • Acid reacts with the mineral calcite • Magnetism---