MINERAL FAMILIES

Aim: Describe the Properties of the Two Major Groups of Minerals: Silicates and

Non-Silicates

• Classified into 7 Groups

• Based upon their chemical composition

I Native Elements:

• consist of a single element

Examples:

Silver Ag,

Copper Cu,

Graphite C

II Sulfides: -

- compounds of metal and sulfur

- Most are heavy with a metallic luster

- examples: Galena, Pyrite, sphalerite

III Oxides: -

- compounds of metals and oxygen

- Contain an oxygen and an element other than Silicon

- examples: Hematite, corundum

IV Halides

- salts made of a combination of metals and the nonmetallic

elements known as halogens.

• - examples: Sodium Chloride

V Carbonates : -

- compounds of metals with carbon and oxygen.

- carbonates dissolve easily in acid.

- examples: calcite (calcium carbonate)

VI Sulfates:

- compounds of metals with sulfur and oxygen

- hydrous sulfates are soluble in water and contain water molecules.

- anhydrous sulfates are less soluble and do not contain water molecules.

VII Silicates:

- compounds of various elements with silicon and oxygen.

- examples: Quartz, clay, talc, mica

- the most abundant group

- make up 90% of Earth’s Crust

- elements that make up are Si and O

- these elements form a unit called a tetrahedron

Tetrahedron

• molecular formula

SiO4

structural formula

The Silicates

• As the mineral forms, more silica tetrahedra are layered on. The weaker the bonds between the layers of tetrahedra, the more likely a mineral is to cleave along those planes.

• The kind of ion that bonds with the tetrahedron will determine the kind of rock forming silicate that is produced – the arrangement of these atoms determines the crystal shape that results

• Because most of the common minerals are silicates, and because silicates are formed by combinations of the silica tetrahedral with other elements,

the silica tetrahedral is the fundamental unit of the earth’s crust.