Minas Gerais is world-famous among mineral collectors because the majority of all semi-precious stones are mined in this state. Many collectors who do not know Brazil make the mistake to think this was actually the name of a mine, translated "General Mines". But actually it is the name of the states and the gemstone centers are Diamantina and Ouro Prêto. Diamantina was once the biggest diamond producer in the world, but today it is famous for rare quartz crystals. There is a small diamond museum, but not a single show mine. As all the show mines are located in a rather small area around Ouro Prêto, we have a separate page listing them:
Minas Gerais is also famous for numerous caves, with most interesting geologic phenomena and extraordinary speleothems. At the moment more than 500 caves are listed in the cave register. An impressive superlative is the longest stalactite of the world at the Caverna Janelão, which is 28 m long. Gruta do Centenário is the deepest cave of Brazil and of the whole southern hemisphere with a vertical range of 481 m.
To the North of Belo Horizonte, a little south of the center of Minas Gerais, is the location of one of the most important Brazilian carbonate karst areas. It is called Lagoa Santa Karst, developed in the limestones of the Sete Lagoas Formation (Bambuí Group), which consists of very pure calcarenites (CaCO3 >94%). The whole area is intensively karstified and shows numerous karst features like numerous coalescent dolines or sinkholes. Other common features are the big linear cliffs, the results of doline evolution, canyons, and blind-valleys. Also many poljes, large lowered plains which are seasonally flooded.
This karst area has hundreds of caves, of which numerous are paleontological sites of great value. They contain specimens of the extinct Pleistocene megafauna, and important vestiges of the pre-historic human occupation of Brazil. In Gruta Lapinha the Danish scientist Peter Wilhelm Lund described 12,000 year old human bones of the Homem da Lagoa Santa (Lagoa Santa Man). He lived in this area from 1835 to his death in 1880.
The region is today in a process of intense urban and industrial development. To protect the natural and scientific values of this region, the Environmental Protection Area (APA) was founded.
Most extraordinary is the quartzite karst of the state. Quartzite is normally not soluble by water, so it does not allow the formation of karst. But here, with high tropic temperatures, frequent rains and much time, the nearly impossible happened, the quartzite was dissolved. The Gruta do Centenário is 3,790 m long and 481 m deep. It is the longest and the deepest quartzite cave of the world.