Minerals Chapter 4

What is a mineral Mineral- a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure. Cubic Tetragonal Hexagonal Orthorhombic Monoclinic Triclinic 4.1

What is a mineral Some minerals form from magma. –Magma- molten material found beneath Earth’s surface. –The type and amount of elements found in the magma determine the type of minerals formed –Slow cooling forms large well defined crystals –Fast cooling forms small crystals 4.1

What is a mineral Some minerals form from a solution –If a solution becomes supersaturated, or overfilled with solute, mineral crystals may begin to precipitate, or drop out of solution –When liquid evaporates the solute is left behind and will crystalize 4.1

What is a mineral Mineral groups- –3000 minerals are found in the earth’s crust –30 of these minerals are common –Most common minerals referred to as rock forming minerals –Most minerals are made of 8 common minerals 4.1

What is a mineral Silicates- contain silicon and oxygen and usually one or more other elements –96% of the minerals on earth are silicates –Feldspar and quartz 4.1

What is a mineral Carbonates- contain one or more metallic elements with a carbonate compound (CO 3 ) –Calcite and dolomite –Primary mineral in limestone, coquina, marble 4.1

What is a mineral Oxide- contain oxygen and a metal –Hematite, magnetite, and uraninite Sulfides- composed of one or more elements with sulfur –pyrite Sulfates- composed of one or more elements with a sulfate (SO 4 ) –anhydrite 4.1

What is a mineral Halides- made up of sodium or fluoride combined with calcium, sodium, or potassium. –Halite (NaCl) Native Element- made up of only one type of element –Silver, copper, gold 4.1

Identifying Minerals Color- –Most notable –Typically caused by trace elements in the compound. –Least reliable clue to mineral identification 4.2 Calcite

Identifying Minerals Luster- the way a mineral reflects light –Metallic luster- reflect light like a metal –Nonmetallic- do not shine like metals Dull, pearly, waxy 4.2Copper

Identifying Minerals Texture- describes how a mineral feels to the touch –Smooth –Rough –Ragged –Greasy –Soapy –Glassy 4.2

Identifying Minerals Streak- the color of a mineral when it is broken into a powder –Use a unglazed porcelain plate –Can only be used with minerals that are softer than the porcelain plate –Varying external color and weathering will not change the streak for a specific mineral. –One of the most reliable test to ID minerals 4.2

Identifying Minerals Hematite and Galena

Identifying Minerals Hardness- a measure of how easily a mineral can be scratched –One of the most reliable test to ID minerals 4.2

Identifying Minerals Cleavage and fracture –Cleavage- mineral will split along one or more flat planes –Fracture- mineral will break with rough or jagged edges Conchoidal fracture- break in arc-like patterns resembling a clam shell 4.2 Mica Obsidian

Identifying Minerals Density and specific gravity –Density- mass per unit of volume D = m/v –Specific Gravity- ratio of the weight to the weight of an equal volume of water at 4 o C 4.2

Identifying Minerals Special Properties –Double refraction- the bending of light as it passes through a mineral –Effervescent- hemically reacts in the presence of an acid –Magnetic –Odor- certain sulfur containing minerals will smell like rotten eggs. –Fluorescence- Glow when exposed to UV light 4.2

Mineral Uses Ores- contain a useful mineral that can be mined for profit. –Mines- used to obtain ores from deep inside the earth’s crust Open-pit- clear land and dig a hole to the mineral –quarry Shaft mining- dig a tunnel to remove the ore 4.2 Copper Mine

Mineral Uses Gems- valuable minerals that are prized for their rarity and beauty. –Rubies, emeralds, diamonds –Certain impurities (trace elements) might make one form of a mineral more valuable than another. Amethyst- purple version of quartz. 4.2