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XXVIT. On Platina and Native Palladium from Brasil, 

 By William Hyde Wollaston, M,D, Sec,R.S* 



Although platina has now been known to mineralogists 

 for more than 6o years, yet it had not been discovered in 

 any other places than Choco and Santa Fe, whence it was 

 originally brought, until' about t\X'o years since M. Vau- 

 quelin discovered it in some gray silver ores from Guadal- 

 canal in Estremadura. In analysing these ores, he found 

 some fragments that contained as much as one-tenth of 

 their weight of platina, but he did not find it accompanied 

 by any of the new metals that have lately been discovered 

 in the Peruvian ore of platina. 



The specimen which I am now about to describe is de-r 

 rived from a third source, and it is rendered the more in- 

 teresting by having grains of native palladium mixed with 

 it. This new mineral has lately been received from the 

 gold mines in Brasil, by H. E. Chev. de Souza Coutinho, 

 ambassador from the court of Portugal, resident in this 

 country ; and I am in hopes that some account of it may 

 be acceptable to the Royal Society, although the analysis 

 must necessarily be very imperfect, from the small quantity 

 to which my experiments have unavoidably been confined. 



The general aspect of tJiis specimen is so different from 

 the common ore of platina, that I could form no con- 

 jecture of what ingredients it might be found to consist. 

 Its appearance was such indeed, as at first sight to induce 

 a suspicion of its not being in a natural state, for it had 

 very much the spongy form which is given to platina from 

 imperfect attempts to render it malleable by means of 

 arsenic. 



One circumstance, however, occasions a presumption 

 that no art has been employed in giving the grains their 

 present appearance ; as upon close inspection many small 

 particles of gold are discernible, but there is none of the 

 magnetic iron sand with which the IV.ruvian ore abounds, 

 nor any of the small hyacinths, which 1 have formerly no- 

 ticed as accompanying that mineralf. 



It is very well known, that the connnon ore of platina in 

 general consists of flattened grains, that appear so much 

 worn at their surface, as to be in a considerable degree po- 

 lished, and the roughness observable in some of the larger 

 grains arises from concave indentations of a reddish brown 



♦ From Philosophical Transactions for 1809, Part II. 

 . I Fhil. Trans, for 1805, p. 318. 



or 



