Minerals are solid, naturally occurring, inorganic compounds that possess an orderly internal structure and a regular chemical composition. A mineral species has to possess these five characteristics to be regarded as scientifically valid.
The first and most basic characteristic of all minerals is that they occur naturally. Minerals are not made or influenced by human activity. However, some minerals, such as diamonds, can be manufactured by humans. Diamonds are nevertheless classified as minerals, because they adhere to the five core characteristics of minerals.
In addition to being formed by a natural process, minerals are stable at room temperature. This simply means that all minerals are solid at normal temperatures and pressures common on the Earth’s surface. This characteristic excludes water from being a mineral because of its liquid state but includes the solid form of water – ice – as a valid mineral.
Minerals are also represented by a chemical composition or atomic structure. Minerals all share a uniquely orderly internal order. The atoms that comprise a mineral are arranged in an orderly repeating pattern.
All minerals possess either a fixed or variable chemical composition. Most minerals are comprised of compounds or various combinations of oxygen, aluminum, silicon, sodium, potassium, iron, chlorine and magnesium.