Minerals

Minerals are naturally occurring substances with their own chemical composition which is formed from various elements. They have a distinctive physical appearance and are defined as hard, inorganic objects with an organised internal makeup. This makeup is an ordered atomic structure which gives minerals their crystalline appearance. 

Minerals range from simple compounds such as chalcanthite to the largest and complex group of minerals known as the silicates. Silicates are mostly comprised of oxygen and silicon plus the addition of other substances such as calcium or magnesium.

Other categories of minerals include sulphates, phosphates and carbonates.

Rocks

Most rocks are formed from silicate minerals. They are usually formed from a combination of minerals and do not have a precise chemical structure. The most common minerals found within rocks include quartz, mica and feldspar. 

Rocks and minerals with a high commercial value are known as 'industrial minerals'. Rocks which are often mined for economic reasons are known as 'ores'.  

Features of minerals

Minerals are defined by a set of criteria which refer to their individual features. Solidity or hardness is one feature but others include density, colour, transparency and cleavage.

These describe the colour, texture and thickness of a particular mineral. Transparency refers to the clarity of a mineral and density is used to describe the weight of a mineral. Cleavage is a term used to describe the breaking of a mineral or crystal along a specific plane.  

Types of minerals

These include minerals which are extensive although only to a certain extent and those minerals which are much rarer and more valuable as a result.

Examples of widespread minerals include:

  • Garnet
  • Gypsum
  • Pyrite
  • Sphalerite
  • Zircon

Then there are those lesser well known minerals which include:

  • Gold
  • Silver
  • Diamond
  • Copper
  • Amethyst

These are a few of the many types of minerals which are uncommon but may have a high value, for example gold and diamonds.

Other types of minerals

There are minerals which do not fit the criteria described in the opening paragraph. There are fewer of these than the solid, inorganic types are mentioned above but it is useful to know about these.

They include soft minerals, unnatural minerals and amorphous minerals.

Soft minerals are used as pigments in paints and are the main constituent in talcum powder.

Unnatural minerals are considered to be substances which have formed as part of the decomposition of artificial materials such as those found in industrial sludge holding pits.

Amorphous minerals are types of minerals which have a poor or non-existent crystalline structure. They still have distinctive physical and chemical properties but lack a solid inner structure due to instant cooling when developing.   

The most common types of minerals in Hawaii are cement, sand, gravel and gemstones.