Intelligence and Miscellaneous Articles. 397 



drate of iron, from which it differs by its great fusibility, its ready 

 solubility in dilute nitric acid, and its reaction with the blowpipe, 

 &c. 



The mean of two analyses gave as its composition — 



Oxide of lead 53-43 



Oxide of copper 15*78 



Vanadic acid 13*41 , 



Arsenic acid 4*64 



Phosphoric acid 0*64 



Chloride of lead 033 



Silica? 116 



Lime 0*54 



Oxide of iron, alumina, &c 3*46 



Argillaceous residue 1*26 



Water 2*70 



97*35 

 From these results the author is induced to suppose that the above 

 mineral contains a double vanadiate of lead and copper, the com- 

 position of which approaches the formula Ph'^V + Cu'^V, or Pb^V 

 + Cu*V. — Ann. des Mines, tom. xiv. 



NEW MINERAL FROM BRAZIL. 



M. Dufrenoy exhibited before the Academy a specimen of a mi- 

 neral from Brazil, which appears to be to the diamond what emery 

 is to corundum, as stated by M. Elie de Beaumont. Among some 

 specimens recently sent to the Ecole des Mines by M. Hoffman, a 

 dealer in minerals, were two which were stated to be hard enough 

 to polish the diamond ; and in fact the hardness of these specimens 

 was found to be superior to that of the topaz. 



This substance was analysed by M. Rivot, mining engineer, who 

 had at his disposal one large fragment weighing 65*760 grs., and 

 several small pieces weighing rather less than 0*50 gr. ; the latter 

 only were analysed. The large fragment appeared to come from the 

 same alluvial formation as that in which the Brazilian diamonds 

 occur. Its edges are rounded by long friction ; but it has not the 

 appearance of a rolled flint. It is of a slightly brownish dull black 

 colour. Viewed with a glass, it appears riddled with small cavities 

 separating very small irregular laminae, which are slightly translu- 

 cent and iridescent. The brown colour is very unequally distributed 

 throughout the mass. On one of the faces the cavities are linear, 

 which gives it a fibrous aspect similar to obsidian. It cuts glass 

 readily, and scratches quartz and topaz; its density is only 3*012. 

 The small fragments subjected to analysis weighed 0*444 gr., 

 0*410 gr. and 0*332 gr. ; their densities were respectively 3*141, 

 3-416 and 3*255. 



These numbers indicate great difference in the porosity of the 

 specimens ; they lead, however, to the conclusion, that the density 

 of the substance is very nearly the same as that of the diamond. 



