ore minerals

ore minerals Ore minerals are economically valuable minerals that through various methods of mining and mineral extraction can be separated from waste and processed to yield valuable commodities. This definition is used, in the strictest sense, by economic geologists and mining engineers to apply only to those minerals that contain the valuable commodity of interest. For example, they do not consider that worthless iron sulphides associated with valuable copper sulphides in a copper deposit are ore minerals. However, the term ‘ore minerals’ is also encountered in petrography, where it refers to any mineral that is opaque to transmitted light when examined in thin section. Ore minerals are found in several of the main chemical classes into which minerals can be classified, including native elements, sulphides, oxides, silicates, arsenides, phosphates, and carbonates.

The simplest ore minerals are the native metals in which the mineral is composed of a single element. The best-known example in this group is native gold, which is the most common ore mineral of this metal. Other metals for which the native form is an important ore mineral include silver, copper, and bismuth. Two or more metals can also combine to form a group of ore minerals called alloys. Electrum, an alloy of gold and silver, is a common mineral in gold–silver deposits, and many of the metals of the platinum group combine with each other, as well as with other metals, to form complex alloys.

The sulphide minerals comprise an important group of ore minerals in which one or more metals combine with sulphur. Simple sulphide minerals are formed when a single metal combines with sulphur. For example, sphalerite and galena (the simple sulphides of zinc and lead), are the world's primary source for these metals. Other rarer simple sulphides are important sources of antimony, arsenic, bismuth, copper, mercury, molybdenum, nickel, and silver. Sulphide minerals in which two metals combine with sulphur are also common ore minerals. Chalcopyrite, a combination of copper, iron, and sulphur, is an important ore mineral for copper and is found in many of its deposits. Other more complex sulphides, formed by the combination of two or more metallic or metalloid elements with sulphur, are called sulphosalts. These minerals are less common than the simpler sulphides and are important as ore minerals in only a few deposits.

Many oxide minerals also constitute economically important ore minerals. Simple oxides, in which a single metal combines with oxygen, are the major ore minerals of iron (magnetite and haematite), tin (cassiterite), manganese (pyrolusite), titanium (rutile), and uranium (uraninite). Hydrated oxides, in which water is incorporated into the chemical structure of the mineral, also provide important sources for several metals, including iron (goethite) and manganese (manganite). Bauxite, the major ore of aluminum, is composed of a mixture of hydrated aluminum oxides (gibbsite, diaspore, boehmite).

Although many metals combine with silicon and oxygen to form silicate minerals, these cannot in general be refined economically because of the large amounts of energy required to extract the metals. There are, however, some metals for which silicate minerals are an important source. For example, the major ore minerals for lithium and beryllium (spodumene and beryl) are silicate minerals.

Bruce W. Mountain