Brazilian Minas Gerais gems

Minas Gerais means general mines, and it is the only place on this map whose name is a mining term. The state has been producing gemstones for three hundred years and it produces more different species in commercial quantity than anywhere else on Earth.

The engine is pegmatite. Eastern Minas Gerais holds one of the world's great pegmatite provinces, granite melts that concentrated the leftover elements nobody else wanted, and the crystal pockets in them are where the gems sit. Tourmaline in every colour the mineral makes. Aquamarine and heliodor and morganite, all beryl. Topaz, both the ordinary kind and the imperial topaz around Ouro Preto, which is a genuine locality-restricted material in sherry, peach and true reddish tones that come from almost nowhere else. Kunzite, chrysoberyl and alexandrite, euclase, brazilianite, which is named for the country and was first described here. And amethyst and agate, from the same Paraná lava province that Uruguay works.

The gold matters too, because it came first. Ouro Preto means black gold, and the eighteenth-century rush that named it built the baroque towns that are now a UNESCO World Heritage Site. The gem trade grew out of the same mining culture and much of it still runs through the same families.

Practically, this is a place to go and buy, and to go and look. Teófilo Otoni is the pegmatite trading town, Governador Valadares is the other, and Ouro Preto has both the imperial topaz and the mining museums. Working pegmatite mines are private, often family held, and go in with somebody who knows the ground rather than on your own.

One warning worth carrying. Imperial topaz and the better tourmalines attract treatment and misrepresentation, so buy from an established house and get a lab report on anything expensive.