Minerals

Unit 3 Notes

What is a mineral?• A mineral must be all of the

following:

• Naturally occurring

• Inorganic solid (not living)

• Definite structure

• Definite composition (what it’s made of)

What is a crystal?

• A crystal is a solid in which the atoms are arranged in repeating patterns

Crystal StructureHere are the six crystal systems that all minerals belong to:•Cubic – sylvite, halite•Hexagonal – emerald, graphite•Tetragonal – wulfenite, zircon•Orthorhombic – topaz, sulfur•Monoclinic – gypsum, mica•Triclinic – kyanite, turquoise

Elements in Earth’s Crust

OxygenSiliconAluminumIronCalciumSodiumPotassiumMagnesiumOther

Name Symbol % By Mass

Oxygen O 46.6%

Silicon Si 27.7%

Aluminum Al 8.1%

Iron Fe 5.0%

Calcium Ca 3.6%

Sodium Na 2.8%

Potassium K 2.6%

Magnesium Mg 2.1%

Others ---- 1.5%

Mineral Composition

• Silicates (Si & O)

• Carbonates (C & O)

SilicatesThe silica tetrahedron consists of four oxygen atoms packed closely around a single silicon atom. Named for its shape (like a 3D pyramid).

How do minerals form?

• 3 Ways:–Cooling of molten rock (lava or magma)

–Evaporation of liquid

–Saturated solutions

Mineral Crystal Size

• Small Crystals – indicates slow cooling of molten rock

• Large Crystals – indicates fast cooling of molten rock

Mineral Identification

• Color – color is the first property you notice – this is usually the 1st step in identification, but the least useful

Quartz and Fluorite

come in many different colors

Mineral Identification

• Hardness – is a mineral’s resistance to being scratched

Moh’s Scale of Hardness

• Scale ranges from 1 to 10

• 1 is softest & 10 is hardest

Factoid

•What is the hardest substance on Earth??

• A diamond is the hardest substance

(10 on Moh’s scale)

1010 DiamondDiamond

99 CorundumCorundum

88 TopazTopaz

77 QuartzQuartz

66 FeldsparFeldspar

55 ApatiteApatite

44 FluoriteFluorite

33 CalciteCalcite

22 GypsumGypsum

11 TalcTalc

Mohs HardnessMohs Hardness ScaleScale

Mineral Identification

• Streak – the color of the powder left when a mineral is rubbed against a hard rough surface (usually unglazed porcelain)

Testing Mineral Specimens

Mineral Identification

• Luster – the way light reflects from a minerals surface

2 Types of Luster

• Metallic – shiny

• Nonmetallic – glassy, brilliant, greasy, oily, waxy, silky, or pearly

Metallic Luster

Pearly Luster(Non-Metallic)Vitreous

Luster(Non-Metallic)

Mineral Identification

• Cleavage – mineral breaks along smooth surface

• Fracture – mineral breaks unevenly (jagged)

Mineral Identification

• Specific Gravity – comparing density of a mineral to the density of water

Mineral Identification

• Acid Test – some minerals give off CO2 (carbon dioxide) when acid is added.

If it’s a carbonate…

Mineral Usage

• Ore – mineral resource mined for a profit

• Gem – mineral that is beautiful, rare, and valuable

Metals

• Metals are elements that have metallic luster, malleability, ductility, and conductivity

Malleability

• the ability of a mineral to be hammered without breaking

Ductility

• the ability to be pulled and stretched without breaking

Conductivity

• the ability to conduct heat or electricity