Physical Geology

2.1

Electrons, Protons, Neutrons, and Atoms

An atom is made up of protons and neutrons in the nucleus and electrons arranged in energy shells around the nucleus. The first shell holds two electrons, and outer shells hold more, but atoms strive to have eight electrons in their outermost shell (or two for H and He). They either gain or lose electrons (or share) to achieve this, and in so doing become either cations (if they lose electrons) or anions (if they gain them).

2.2

Bonding and Lattices

The main types of bonding in minerals are ionic bonding (electrons transferred) and covalent bonding (electrons shared). Some minerals have metallic bonding or other forms of weak bonding. Minerals form in specific three-dimensional lattices, and the nature of the lattices and the type of bonding within them have important implications for mineral properties.

2.3

Mineral Groups

Minerals are grouped according to the anion part of their formula, with some common types being oxides, sulphides, sulphates, halides, carbonates, phosphates, silicates, and native minerals.

2.4

Silicate Minerals

Silicate minerals are, by far, the most important minerals in Earth’s crust. They all include silica tetrahedra (four oxygens surrounding a single silicon atom) arranged in different structures (chains, sheets, etc.). Some silicate minerals include iron or magnesium and are called ferromagnesian silicates.

2.5

Formation of Minerals

Most minerals in the crust form from the cooling and crystallization of magma. Some form from hot water solutions, during metamorphism or weathering, or through organic processes.

2.6

Mineral Properties

Some of the important properties for mineral identification include hardness, cleavage/ fracture, density, lustre, colour, and streak colour.

calcite

biotite

pyrite

gypsum

galena

orthoclase

hematite

graphite

magnetite

quartz

fluorite

olivine