May 24 2014
Mineral oxidation is a chemical reaction, which takes place in a mineral upon exposure to oxygen, resulting in a change in the chemical composition. It takes place through weathering, which is a breakdown of minerals, rocks, and soil through contact with biota, water, and atmosphere.
The chemical oxidation of a number of metals occurs in the weathering environment, especially when oxygen combines with other elements in the rocks to form new types of rock. These new substances are generally softer and easier for other forces to break apart.
Oxidation during weathering involves the addition of oxygen and the destruction of old compounds. For instance, oxide minerals are produced when iron combines with oxygen. When minerals in the rocks oxidize, they become less resistant to weathering.
Oxidation of iron destroys limonite or hematite and siderite to produce carbon dioxide.
Similarly, sulfuric acid is produced when marcasite or pyrite is destroyed through oxidation. This gives the affected rocks a reddish-brown color on the surface, which in turn weakens and crumbles the rock.
In all these cases, the original mineral is destructed to produce one or more new minerals through oxidation. Many other metallic ores and minerals oxidize/hydrate to form colored deposits, such as chalcopyrites.
Mineral oxidation is more active in the presence of moisture, which results in the formation of hydrated oxides, i.e. minerals containing magnesium and iron.
Sources and Further Reading