428 -^ ScientiJIe Jntelligence-^Geohgy. 



of Sciences has received from M. Claussen, a geologist wlio lias re- 

 sided for twenty years in the Minas Geraes of Brazil, many geolo- 

 gical notices of the province. We shall now dwell only upon the one 

 bearing upon the true mineralogical habitat of the diamond. Towards 

 the beginning of the year 1839, diamonds were discovered in the 

 psammite sandstone (le gres psammite) of the Serro do Santo Antonio 

 de Grammagoa. This mountain is composed of great beds of sand- 

 stone (gr^s) which have a perfect resemblance to itacolumite ;* but 

 their highly inclined beds, reposing immediately upon Macigno, a 

 rock of the transition series, leaves no room for doubt as to their 

 identity with the psammetic sandstones of Abaite (Abaethe). Those 

 who made the discovery procured a great number of diamonds, be- 

 cause the rock was very soft ; but, as they went deeper, it became 

 harder, and consequently more difficult to work. The immensenum- 

 ber of individuals, who were attracted from all quarters, to the num- 

 ber of upwards of two thousand, and who laboured without either 

 order or place, caused a portion of the mountain to crumble away 

 before them, the debris of which still yields a profit by the extracting 

 of diamonds after pounding. Specimens of the rock, with imbedded 

 diamonds, are by no means rare ; although the miners nevertheless de- 

 mand a high price for them, because by completely pounding them, 

 they hope to find those large diamonds with which their imagination 

 fills them. Matters are only made worse, if the purchaser be a 

 stranger, for then they argue that he must know what the specimens 

 contain, and cannot conceive how any one should offer a large sum 

 of money from mere curiosity. The diamonds are found imbedded 

 in the psammite sandstone ; in the itacolumite sandstone they are 

 sometimes discovered between the plates of talc, very much as gar- 

 nets are in mica-slate. In the museum of Rio Janeiro, there is a 

 roundish diamond of very considerable size, which very distinctly re- 

 tains the marks of grains of sand imprinted upon it. 



Among the specimens which M. Claussen has seen, there is rather 

 a remarkable one in the possession of M. Mallard, a French gentle- 

 man settled at Ouro Preto ; it is a small piece of pseudomorphosed 

 sandstone, having very much the aspect of itacolumite, about two 

 inches long and one broad, and contains a diamond weighing about 

 two grains, and crystallized in the shape of a roundish octahedron. 

 The owner demands L.125 for this specimen ! Another remark- 

 able specimen belongs to a Brazilian merchant of Rio Janeiro : it is 

 a piece of yellowish sandstone, about the size of the fist ; It contains 



* The itacolumite is a granular slaty compound of quartz and talc : The so- 

 called flexible sandstone of Br^U is a vwiety of itacolumite. — Edjt» 



