What are Minerals?
Minerals are natural, inorganic substances, composed of the atoms of either one single chemical element or a number of different elements. There are over 4,000 different minerals, and each one is distinguished by its chemical composition (the particular ratio of its chemical elements) and its crystal structure. Nearly all minerals are crystalline: the atoms are arranged in a regular pattern; when allowed to grow freely, they form symmetric crystals with flat faces.
Rock-forming and Ore Minerals
Minerals are in all the rocks of the Earth. They can be found wherever rocks have been exposed, either naturally or by man. Some minerals are rich in those metals we use in our everyday lives, and we exploit these as ores.
ROCK-FORMING MINERALS
Most minerals that make up the bulk of rocks and veins are neither metallic nor noticeably heavy, and many are not particularly colourful. There are important exceptions, however, and some of the most richly coloured are gem minerals that are beautiful, durable, and rare.
ORE MINERALS
Ores and their secondary minerals frequently occur in mineral veins, which are sheet-like structures that result when minerals fill fractures within existing rocks. Many ore minerals look metallic, and some are noticeably heavy. Secondary minerals may be formed when primary ore minerals are altered by rain and groundwater. They are often brightly coloured, and some may themselves be of economic value