Calamine brass slowly phased out as zinc smelting techniques were developed in Europe, which produced metallic zinc more suitable for brass production than calamine. However, the conversion away from calamine brass manufacture was slow; a British patent was awarded to William Champion in 1738, but the alloying of metallic zinc and copper to produce brass was not patented until 1781 (by James Emerson), and calamine brass mills persisted in South Wales until as late as 1858. The slow diffusion of this technology was probably the result of economic factors. Calamine brass Calamine brass is brass produced by a particular alloying technique using
Coltan Coltan Coltan (short for columbite–tantalites and known industrially as tantalite) is a dull black metallic ore, from which the elements niobium and tantalum are extracted. The niobium-dominant mineral in coltan is columbite (after niobium's original American name "columbium"), and the tantalum-dominant mineral is tantalite. Tantalum from coltan is used to manufacture batteries for electric cars, and in tantalum capacitors it is used in electronic products. Coltan mining has helped to finance serious conflict in the Democratic Republic of Congo, for example the Ituri conflict and the Second Congo War. Approximately 71% of global tantalum supply in 2008 was newly mined,