The earliest organized prospecting and mining in Tanzania took place during the German colonial period, beginning with gold discoveries in the Lake Victoria region in 1894. Mining began at the Sekenke Mine in 1909. After 1930, gold production was substantial and increased steadily until World War II. By 1967, the gold industry had declined to insignificance, only to revive after 1974-75 when the world gold price increased greatly. Beginning in April 1990, the Bank of Tanzania began buying gold at the world market price through commercial banks, paying miners in Tanzanian shillings calculated at the parallel-market rate for the US dollar rather than at the official rate.
Diamond mining, which had been relatively minor prior to 1940, received a major boost with discovery of the Mwadui Mine in 1940.
Besides gold and diamonds, which have long been the mainstays of mineral production, mining of other commodities has been relatively modest, namely for copper, lead, phosphate, coal, kaolin and gemstones.
In the late 1980's, the government attempted to capture the revenues being generated from gem mining by licensing private companies to buy, cut and export gemstones being produced by small-scale miners. Coloured gemstones (excluding diamonds) are an increasingly important mineral product. In 1989, small miners produced about 10 tonnes of precious and semi-precious stones. Tanzania's most famous gem is tanzanite, a sapphire-coloured variety of zoisite discovered in 1967. Other important gemstones are ruby, sapphire, emerald, garnets and lesser quantities of zircon, tourmaline and other minerals.
In the late 1990's, several mining companies from Canada, United Kingdom, Australia and South Africa arrived in Tanzania, interested in gold exploration and development. From 2000, production of gold at an industrial scale is growing, especially from the Geita (AngloGold/Ashanti) and Bulyanhulu (Barrick) mines.