Tantalitecolumbite

Tantalitecolumbite refers to the solid-solution series of oxides formed by tantalite and columbite, two closely related minerals that share a common structural framework. The general composition is (Fe, Mn)(Nb, Ta)2O6, in which iron and manganese occupy one site and niobium and tantalum occupy the other. The proportion of tantalum to niobium distinguishes the two end-members: tantalite is Ta-rich, columbite Nb-rich, and many natural samples fall along a continuum known as tantalite-columbite or colloquially as coltan when mined as an ore.

The minerals are typically dark, heavy, and opaque with a submetallic luster. They occur as coarse grains in granitic pegmatites and greisen, and can also be present in alluvial placer deposits derived from primary sources. They are commonly associated with other Nb–Ta minerals and with tin, tungsten, and rare earth minerals. The presence of tantalum makes tantalite-columbite economically important because tantalum is a critical metal used to produce high-p purity tantalum oxide and tantalum capacitors.

Ore deposits are concentrated in several regions, with Africa historically supplying a large portion of global production, particularly from the Great Lakes region, as well as deposits in Australia, Canada, Brazil, and China. Because tantalum is valuable for electronics, tantalite-columbite ores are often referred to in mining as coltan ore, a term frequently encountered in discussions of supply and ethical sourcing.

The name derives from tantalum, named after Tantalus in Greek mythology, and columbite, linked to the historical name for niobium (columbium). The two minerals form a continuous series and are not always easily distinguished in ore samples.