Diamond District (Port. Districto Diaman-tino), a district in Brazil, so called from the diamond grounds for which it has long been celebrated, situated in the Serra do Frio, in the province of Minas Geraes. It extends from E. to W. between lat. 17° and 19° S., and is watered by the Jequitinhonha and several tributary streams of the Rio Sao Francisco. In 1725 Sebastiao Leme do Prado discovered the Manso, a small affluent of the Jequitinhonha, and found some white stones which were sent as specimens to the court of Portugal, where, however, they at first attracted little attention. After an interval of three or four years, Bernardo da Fonseca Lobo penetrated into the hitherto unexplored serras, and discovered similar stones, one among which was of extraordinary size; but as no one knew the value of the gems, they were frequently used as counters at play. A certain ouvidor of the province, who had been in India, perceiving that they were diamonds, purchased a large number at a merely nominal price, and returned to Portugal, about the same time when Almeida, first governor of Minas Geraes, informed the court of the real nature of the stones. Adventurers hastened to profit by the discovery; but discord soon sprang up among them, and quarrels ensued which often ended in bloodshed.
By letters patent, issued in February, 1730, the diamonds were declared crown property; but the liberty to continue the search for gems was purchasable at the rate of 20 milreis ($10) for each negro engaged for the purpose. This impost was soon after increased to 40, and finally to 50 milreis. The crown profited little by these contracts; and in 1771 the government placed the management of the mining under the surveillance of officers specially appointed for the charge, employing at the same time 5,000 negroes at the works. A decree was issued prohibiting the search for gold within the limits of the diamond region, all the approaches to which were guarded by soldiers; while stringent laws were passed to provide for the registering of the inhabitants, the admission of settlers, the erection of inns and shops, and the punishment of infringements of the government monopoly. In pursuance of a law passed in 1873, the diamond mines now belong exclusively to private individuals. A singular uniformity has been observed respecting the diamond grounds of this district. The same cubic mass will yield in washing pretty nearly the same number of carats, whether of large or small diamonds.
Though very large gems do not abound in Brazil, some of considerable dimensions have at times been found. - For the product of these diamond mines, see Brazil, vol. iii., p. 221; and for the mode of working them, see Diamond.