DIAMOND: OCCURRENCE IN BRAZIL 171 



previously considered, the diamantiferous deposits may be distinguished as river-, valley- 

 and plateau-deposits. The discovery of diamonds in Parana was accidental ; the stones 

 found were invariably small, rarely exceeding a carat in weight ; they were usually, however, 

 •of good colour and lustre. Systematic search was undertaken a few years ago, but the yield 

 was small and unremunerative, in spite of the considerable amount of gold present ; it was, 

 therefore, soon abandoned. The stones here are supposed to have been washed out of the 

 Devonian sandstone through which the rivers mentioned above flow, and the sandstone 

 itself may have been formed from the weathered debris of itacolumite. 



In the State of Goyaz, on the western border of Minas Geraes, diamonds have been 

 found in the Rivers Guritas, Quebre-Anzol, S. Marcos, and Paranayba. The upper part of 

 the River Araguaia, bordering on the State of Matto Grosso and its right tributary the Rio 

 Claro (lat. 16° 10' S., long. 50° 30' W., of Greenwich), and others in Goyaz are specially 

 rich. The yield from these rivers has been considerable, the diamonds found up to the year 

 1850 in the Rio Claro alone amounting to an aggregate weight of 252,000 carats valued 

 at de400,000. 



In the State of Matto Grosso diamonds have been searched for in some of the rivers 

 as far as the Bolivian frontier, and in places a rich yield has been obtained. The majority 

 of the stones have been found in the neighbourhood of Diamantino (not to be confused with 

 Diamantina, formerly Tejuco, in Minas Geraes), in the district of the source of the Paraguay 

 and its tributaries, especially the Rio Cuyab^, a tributary on its right bank (lat. 15" 45' S., 

 long. 56° W., of Greenwich). The stones from here are usually small and often coloured, 

 some, however, are of the purest water ; they are distinguished by the possession of a very 

 brilliant surface, a feature which is usually absent from Brazilian stones. Up to 1850 the 

 State of Matto Grosso had yielded diamonds to the weight of about 1,191,600 carats valued 

 at ^1,850,000. 



The geology of Goyaz and Matto Grosso is but little known ; travellers, however, state 

 that itacolumite is widely distributed ; we may therefore assume that the occurrence of 

 diamond in these States agrees in all essential points with that in Minas Geraes. 



With respect to productiveness, the State of Bahia stands second to Minas Geraes ; 

 while the latter, however, is now for the most part exhausted, in the former new and rich 

 deposits have been discovered. Thus the present yearly production of Bahia exceeds that 

 of Minas Geraes, but the reverse is the case when the total production of the two States is 

 ■compared. 



Diamonds had been discovered in Bahia as far back as the year 1755 ; further search, 

 however, was at that time prohibited by the Government in the fear that the agricultural 

 prosperity of this fertile State might suffer. In spite of this prohibition more and more 

 finds were made, until at the beginning of the nineteenth centm-y the production was quite 

 considerable. It has continued to grow, until now the yearly output exceeds that of Minas 

 Geraes. 



The first finds were made on the eastern slopes of the Serra da Chapada and, north 

 of this, in the Serra do Assuaria, which forms the continuation northwards of the Serra do 

 Espinhapo, a range of mountains stretching across the greater part of Minas Geraes and 

 passing through the district of Diamantina. The stones are found in sands and gravels in 

 the water-courses, and are accompanied by the minerals which constitute the most important 

 associations of diamond at Diamantina, namely, the oxides of titanium and of iron, 

 tourmaline, and quartz (rock-crystal). In addition to these are a few others, which do not 

 occur in Minas Geraes. In a sample of diamond-sand from the Serra da Chapada, Damour 

 determined the following minerals : pebbles of rock-crystal, crystals of zircon, tourmaline, 



