Minerals are solid materials that have been formed by nature. All types of rock consist of mixtures of minerals. Minerals are frequently crystalline in form. Crystals are multi-faceted or convex in shape. Minerals take on these forms because the arrangement of the atoms is different in each of them. Over 4,200 different minerals have been discovered on Earth so far. Minerals can contain materials that are useful to man, like metals or salts. Gemstones are minerals that are particularly beautiful, hard and – above all – rare.
