From Belo Horizonte it takes one and a half hour to reach it, through a winding but pleasant road.
Ouro Preto was the capital of Minas Gerais from 1822 until 1897, when the needs of the government outgrew this town in the valley. The state government was moved to the new, planned city of Belo Horizonte.
There are several Imperial Topaz Mines in the area, apart from many nameless small open pits. The most important mines are Mina do Vermelhão, in Saramenha and the Capão Mine. This last one is the largest mine for Imperial Topaz in the world. It is an open cast mine, where weathered topaz-quartz-calcite veins are mined. The gravel is transported by a dredge bucket to the hydraulic washing station. The clay is removed with huge water cannons and the material is transported to a sorting a belt, where the crystals are picked out by workers. They process tons of clay to get a few dozen topaz crystals per day (2 cubic meters of rough for 1ct of gem).
I am not a miner and I have only been inside a handful of mines in my life. So I can't say how amazing it is to dig your own stone, but I can say how great it is to be able to buy from the source. In Ouro Preto, when you visit a mine like Capão, you go as a tourist, you watch, take pictures, have a lecture and get a peak at beautiful overpriced crystals. It is quite interesting but from a business point of view, it's prohibitive. So we rely on the good old small mines. It is quite gratifying to get lucky and see a nice little crystal being found in front of your eyes and then try to bargain a fair price for it. (The prices are crazy in every little corner of the world.)