Ch 4. Minerals

What is a mineral?Naturally occurringInorganicSolidSpecific chemical compositionDefinite crystalline structure

Naturally OccurringMinerals are formed by natural processesThey are NOT man made

InorganicThey are not aliveSalt is a mineralSugar is not because it was harvested from a

plant.

SolidSolids have a definite shape and volume

Specific chemical compositionEach mineral has a unique “recipe”

Quartz = SiO2

Calcite = CaCO3

Some minerals consist of a single elementCopper (Cu), Silver (Ag), Sulfur (S)

Definite Crystalline StructureAtoms are arranged in a regular geometric

patternPattern is repeatingMinerals that form in an open space may

grow into a single, large, well-defined crystalThis is rareMost crystals form in a restricted space so

their internal structure is not as obvious

Formation of mineralsFrom Magma

Magma cools as it rises toward the surface of the Earth

Compounds in the magma begin to interact chemically

Magma cooling slowly results in LARGER crystal sizes

Magma cooling very quickly results in SMALLER crystal sizes

Formation of MineralsFrom solution

When a solution cannot dissolve anymore of a substance it is considered supersaturated

This may cause mineral crystals to precipitate out of the solution

The same can happen if the liquid evaporates

Mineral GroupsNumbers

Approximately 3000 known mineralsAbout 30 are considered common10 make up 90% of the Earth’s crust

Oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium

SilicatesConsist of 1 silicon atom, 4 oxygen atoms and

usually one or more other elementsStructure is called a tetrahedron. (pyramid)Oxygen atoms can bond with one another in

several different waysExample – Olivine – Mg2SiO4

CarbonatesConsist of one or more metallic elements and

a carbonate group CO3Example – Calcite – CaCO3Carbonates are the primary minerals found in

limestone and marble

OxidesCompounds of oxygen and a metalExamples – hematite and magnetite FeO3Both are common and good sources of iron

SulfidesCompounds of sulfur and one other elementExample – FeS2 - Pyrite

SulfatesContains the sulfate compound SO4Example – Anhydrite – CaSO4

HalidesMade up of Chloride and Fluoride along with

Calcium, Sodium, or PotassiumExample – Halite – NaCl (salt)

Native elementsMade up of a single elementExample – Silver and Copper