Introduction to Minerals Potassium Fedspar Quartz

What is a mineral??? Naturally ocurring Inorganic Crystalline solid Defined chemical composition

What is a mineral??? Naturally ocurring Inorganic Crystalline solid Defined chemical composition -Building blocks of rocks, i.e. Rocks are made of minerals

Physical properties of minerals Crystal Form -Minerals have different shapes because of the special arrangement of atoms within them.

Physical properties of minerals Crystal Form -Minerals have different shapes because of the special arrangement of atoms within them. -Size increases with time of crystallization.

Some minerals exhibit better crystalline form

Physical properties of minerals (continued) Luster Appearance of a mineral in reflected light Two basic categories Metallic Non-Metallic

Physical properties of minerals (continued) Luster Appearance of a mineral in reflected light Two basic categories Metallic Non-Metallic Other terms: vitreous, silky, earthy

Galena is a lead sulfide (PbS) that displays metallic luster

Physical properties of minerals (continued) Color Generally an unreliable diagnostic property Highly variable for a given mineral due to slight changes in mineral chemistry

Physical properties of minerals (continued) Color Generally an unreliable diagnostic property Highly variable for a given mineral due to slight changes in mineral chemistry Exotic colorations of some minerals produce gemstones

Physical properties of minerals (continued) Color Generally an unreliable diagnostic property Highly variable for a given mineral due to slight changes in mineral chemistry Exotic colorations of some minerals produce gemstones

Physical properties of minerals (continued) Streak Color of a mineral in its powdered form Helpful in distinguishing different forms of the same mineral

Physical properties of minerals (continued) Streak Color of a mineral in its powdered form Helpful in distinguishing different forms of the same mineral Hardness Resistance of a mineral to abrasion or scratching All minerals are compared to a standard scale called the Mohs scale of hardness

Relative hardness… —Rubies & Sapphires —Our teeth! —TUMS! micas

Streaking a mineral… Streak Streak color unglazed ceramic

Physical properties of minerals (continued) Cleavage Minerals will break in a certain direction where the bonds between atoms are not strong. Produces flat, shiny surfaces

Physical properties of minerals (continued) Cleavage Minerals will break in a certain direction where the bonds between atoms are not strong. Produces flat, shiny surfaces Described by: Number of planes Angles between adjacent planes

Three examples of perfect cleavage – fluorite, halite, & calcite

Some more cleavage examples… Micas—one plane of perfect cleavage, can peel off sheets!

Physical properties of minerals (continued) Fracture -Minerals that do not have cleavage will fracture when they are broken. -If the fracture has a smooth, curved surface it is called a conchoidal fracture.

Conchoidal fracture examples…

Physical properties of minerals (continued) Other properties Magnetism Reaction to hydrochloric acid Malleability Double refraction Taste Smell

Acid Test Cool….

To Summarize… -Minerals are crystalline, inorganic, naturally occurring solids -Rock = composed of minerals -Minerals distinguished by physical properties: -Form -Luster -Color -Streak -Hardness -Cleavage/Fracture