Oxide minerals are compounds of metals or metalloids with oxygen, while hydroxides contain the OH group. This class includes more than 250 mineral species.

Some minerals from this class are very significant in the construction of Earth's crust. Oxide minerals are primarily characterized by relatively high hardness and density, and they are resistant to wear. They often occur as accessory (secondary) minerals in igneous and metamorphic rocks and as resistant detrital (transported) grains in sediments. In contrast to oxides, hydroxides are softer, have lower hardness, and generally appear as secondary products of weathering.

Many oxide and hydroxide minerals are components of well-known ores from which economically important black and colored metals are extracted. Examples include magnetite, hematite, and limonite (a mixture of which the most important components are goethite and lepidocrocite) as iron ores; cuprite as a copper ore; chromite as a chromium ore; cassiterite as a tin ore; brucite as a magnesium ore; while ilmenite and rutile are titanium ores. Pyrolusite and psilomelane (a mixture of manganese oxides, with romanechite dominating, and others such as cryptomelane, manganite, todorokite) are ores of manganese. Bauxite, a mixture of several minerals including the most important ones gibbsite, diaspore, and boehmite, is an aluminum ore. Other minerals in this class are important raw materials in the chemical and pharmaceutical industries, are used in high technologies, or are used in construction.