Winning of Diamond

In older times, up to the beginning of the 18 century, most diamonds came from India. In 1725 the situation changed. Considerable deposits were discovered in Brazil, Minas Gerais, where now the town of Diamantina is situated. After the Brazilian 

1) Breccia is a coarse-grained rock composed of angular broken rode fragments held together by a mineral cement. 

The town was for a long time the world center for the winning of diamonds and trading in the valuable precious stones. On top of the famous mine Big Hole , a yellow ground was found, which was a weathering product of the underlying kimberlite, called the blue ground. The mine was worked from 1871 to 1908 with simple methods, but in spite of that a depth of 1070 m was reached. In aU 14.5 million carats of diamond (2900 kg) were obtained. For this extraction a rock quantity of about 24 million tonnes of kimberlite had to be broken. 

F re 39.6 One man-one machine, a drilling technique in diamond mines. (Reprinted with permission of Atlas Copco Rock Drills AB, Sweden.) 

---