How Are Minerals Identified? Minerals are identified by their properties. Color Luster Hardness Streak Density Crystal Shape Cleavage and Fracture Special Properties, such as magnetism, smell, taste and radioactivity

Color Usually the first and most easily observed Not a reliable way to identify a mineral - Some minerals are the same color as others - Some minerals can have many colors ROSE QUARTZ QUARTZ SMOKY QUARTZ

Luster General appearance of a mineral surface in reflected light Glassy-Obsidian

Examples of luster Metallic Vitreous: similar to glass Resinous: resembles the way plastic reflects light Pearly: resembles the way pearls shine Greasy: resembles the way petroleum jelly or a greasy surface reflects light Silky: resembles the way silk reflects light Earthy: dull, may be rough or dusty Waxy Adamantine: resembles the way a diamond shines Fibrous – looks like fibers Pitchy – looks like tar

Hardness Resistance to scratching by different items; “scratchability” Mohs Hardness Scale is used to determine the hardness of minerals by comparing them to substances of known hardness: < 2 fingernail 3 penny ~ 5 Steel of a pocket knife 5.5 Window Glass 6.6 Steel of a file 7 Quartz crystal

Mohs Mineral Hardness Scale 1) Talc 2) Gypsum 3) Calcite 4) Flourite 5) Apatite 6) Feldspar 7) Quartz 8) Topaz 9) Corundum 10) Diamond Softest 1 9 5 2 6 10 3 7 Hardest 4 8

Streak The color of a finely powdered mineral Determined by rubbing the mineral on a piece of unglazed porcelain (streak plate)

Density The amount of matter in a given space Specific Gravity is the comparison of a substance’s density to the density of water

Crystal Shape Minerals have a characteristic crystal shape resulting from the atomic packing of the atoms when the mineral is forming

Cleavage and Fracture Cleavage is the tendency of a mineral to split or crack along parallel or flat planes. Fracture occurs when a mineral breaks at random lines instead of at consistent cleavage planes. BIOTITE QUARTZ Obsidian 1 Direction of Cleavage No Cleavage Conchoidal Fracture

Fracture

Special Properties Magnetism (Magnetite) Glowing under ultraviolet light (Fluorite) Taste (Halite) Smell (Sulfur) Reaction to HCl (Calcite) Double refractive - a thin, clear piece of calcite placed over an image will cause a double image Radioactivity - minerals containing radium or uranium can be detected by a Geiger counter

Economic Importance of Minerals Minerals are in many things we see and use everyday such as; bricks, glass, cement, plaster, iron, gold

Every American Requires 40,000 Pounds of New Minerals per Year At this level of consumption the average newborn infant will need a lifetime supply of: - 795 lbs of lead (car batteries, electric components) - 757 lbs of zinc (to make brass, rubber, paints) - 1500 lbs of copper (electrical motors, wirings - 3593 lbs aluminum (soda cans, aircraft) - 32,700 lbs of iron (kitchen utensils, automobiles, buildings) - 28,213 lbs of salt (cooking, detergents) - 1,238,101 lbs of stone, sand, gravel, cement (roads, homes)