Minerals are solids with a definite (mostly inorganic) chemical composition which are formed by natural processes. They are extremely important to the geologist as they form the 'building blocks' of rocks. So far, approximately 3500 distinct mineral species have been discovered and authenticated, although each year a few more new minerals are added to this list. Minerals can exhibit a bewildering variation in chemical composition, crystal form, colour, size and other physical properties; some of the more attractive minerals will be familiar to many people because their fine colours and reflective properties allow us to use them in jewellery and other ornamental materials. However, to the geologist, minerals are also extremely important because through the study of their occurrence, formation, properties and use (the subject of mineralogy) we gain an important insight into how a rock may have formed. The type of information we can derive is varied, for instance:

- was the rock formed deep in the Earth or at a shallow depth?

- was the rock once molten or did it form from an aqueous fluid?

- did it form at high or low temperatures?

- has it been weathered or otherwise altered after it first formed?

- does it have some economic value?

Minerals are also crucial in our everyday life as they are the source for a wide range of substances; you only need to take a quick look around to see how much material has been derived from minerals in the Earth. Such materials include metals (for example gold, copper and iron), materials for the chemicals industry (salt, fertiliser, sulphur), ceramics (clay) and construction (calcite for cement, gypsum for plaster). Each year we need more and more of these to satisfy our increasing demands, yet future deposits are either becoming increasingly hard to find or are located in areas where mining may conflict with other activities. It is the role of the geologist and earth scientist to discover the resources for the future and to ensure that they can be exploited in the most efficient and environmentally friendly way possible.

The examples shown here are of some representative minerals, including the form in which they occur, and some important aspects associated with their extraction.

Geology Department, Royal Holloway University of London, Egham Hill, Egham, Surrey,
TW20 0EX
Tel: +44 (0)1784 443581 Fax: +44 (0)1784 471780