Oxide minerals are noted for containing metallic alloys or elements. The unique properties and composition of oxides make minerals in the group highly prized among collectors.
Oxides are compounds which contain at least one oxygen atom bonded to another element. Thus, minerals are classified into the oxide category if they have a structure containing oxygen and at least one other metallic element. As a result, the structure of oxide minerals is dominated by metallic atoms present in between larger oxygen atoms. Structures of individual Oxide compounds vary but always have the aforementioned properties (note that minerals with more intricate anions, such as quartz, are grouped in separate classes for classification purposes). The structure of Cuprite, a copper oxide, is shown to the right. Oxides vary widely in properties but often have a distinctly high specific gravity and hardness due to their content of the metal. Many oxide minerals are noted for a metallic, brass-like luster desirable among collectors. However, some minerals in the class exhibit gem-like clarity and luster desired by both collectors and gemstone connoisseurs alike. Oxide minerals also have chief economic importance and comprise parts of rock and ore mined for metals. In particular, zinc, iron, titanium, and manganese are metals with the most economical significance found in oxide zones. Notable examples of oxides include Cuprite, Goethite, Hematite, Rutile, Spinel, and Zincite. Examples:
Simple Oxides - Oxides which contain Oxygen and one another metal
Cuprite
Zincite
Hematite group
Corundum
Hematite
Rutile group
Rutile
Pyrolusite
Cassiterite
Uraninite
Complex Oxides - Oxides which contain Oxygen and multiple other metals
Spinel group
Franklinite
Magnetite
Spinel
Brucite
Manganite
Geothite
References: Mungall, J.E. “Mining Geology | Magmatic Ores.” Encyclopedia of Geology, by Richard C. Selley et al., Elsevier, 2005, pp. 637–645. Post, Jeffrey E. “Manganese Oxide Minerals: Crystal Structures and Economic and Environmental Significance.” PNAS, National Academy of Sciences, 30 Mar. 1999, www.pnas.org/content/96/7/3447.