The chemistry of minerals

Abstract

Matter may exist in three states: solid, liquid and gaseous. A mineral is a naturally occurring inorganic substance which has a definite chemical composition, and which commonly, but not always, is crystalline. Most minerals are solid, but some ‘minerals’ such as native mercury are normally liquid in their natural state, and others, such as natural gas, are gaseous. Gases and liquids are termed fluids; that is, they flow, unlike solids, under the action of gravity at atmospheric temperature (t)and pressure (p); solids may flow under the influence of gravity but at higher t and p. A gas will entirely fill the space containing it, whereas a liquid may not, but may be bounded by an upper, horizontal surface. Most pure substances can exist in all three states depending upon the combination of temperature and pressure acting on the mineral. At specific temperatures, called melting points, many minerals melt to form liquids, although some may actually be decomposed by the heat before reaching their melting points. A sublimate is formed by the direct condensation of a gas into a solid.