section_path: Classification/Non-silicates/Oxides
section_name: Oxides
paragraph_text: Oxides
  
  Oxide minerals are divided into three categories: simple oxides, hydroxides, and multiple oxides. Simple oxides are characterized by O as the main anion and primarily ionic bonding. They can be further subdivided by the ratio of oxygen to the cations. The periclase group consists of minerals with a 1:1 ratio. Oxides with a 2:1 ratio include cuprite (Cu O) and water ice. Corundum group minerals have a 2:3 ratio, and includes minerals such as corundum (Al O), and hematite (Fe O). Rutile group minerals have a ratio of 1:2; the eponymous species, rutile (TiO) is the chief ore of titanium; other examples include cassiterite (SnO; ore of tin), and pyrolusite (MnO; ore of manganese). In hydroxides, the dominant anion is the hydroxyl ion, OH. Bauxites are the chief aluminium ore, and are a heterogeneous mixture of the hydroxide minerals diaspore, gibbsite, and bohmite; they form in areas with a very high rate of chemical weathering (mainly tropical conditions). Finally, multiple oxides are compounds of two metals with oxygen. A major group within this class are the spinels, with a general formula of X Y O. Examples of species include spinel (MgAl O), chromite (FeCr O), and magnetite (Fe O). The latter is readily distinguishable by its strong magnetism, which occurs as it has iron in two oxidation states (Fe Fe O), which makes it a multiple oxide instead of a single oxide.