Identifying Minerals o Properties Color Luster Streak Density

Identifying Minerals o Properties: Color, Luster, Streak, Density, Hardness, Cleavage, Fracture, and Special Properties

Color o The same mineral can come in a variety of colors n o o Ex. quartz Impurities & other factors can change mineral appearance Color is not the best way to identify minerals

Luster o Describes how a surface reflects light n o Ex. shiny/dull Metallic- minerals containing metals are often shiny

Luster Nonmetallic- not as shiny o Examples of Nonmetallic n n n Vitreous- glassy, brilliant Silky-fibrous Resinous-plastic Waxy- greasy, oily Pearly- creamy Earthy- rough, dull

Streak o o Color of mineral in powder form Observed by rubbing a mineral against a piece of unglazed porcelain called a streak plate Streak doesn’t vary like color & is often different than a mineral’s color More reliable than color

Cleavage and Fracture

Cleavage and Fracture- ways the mineral breaks apart, determined by arrangement of atoms.

Hardness o o Minerals resistance to being scratched Mohs’ Hardness Scale: Ranks minerals from softest to hardest Talc- softest known mineral Diamond- hardest known mineral

Hardness

Mohs Hardness Scale o o o o o Talc Gypsum Calcite Fluorite Apatite Orthoclase Quartz Topaz Corundum Diamond 1 2 3 4 5 6 7 8 9 10 Softest known mineral fingernail can scratch it scratched by copper penny easily scratched by steel knife can be scratched by steel knife can scratch window glass can scratch steel can scratch quartz can scratch topaz hardest known mineral

Density o o o mass (how heavy it is) per unit volume (how much space it takes up) D= M/V Density remains same regardless of sample size Mass determined using balance Volume determined using water displacement method. Ex: gold is heavier than pyrite (fools gold)