, ON PLATINA. J29 



that platina had been discovered in Siberia; but this has 

 no more been confirmed, than that spread fifteen years ago, 

 of its existence in a ferruginous sand at St. Domingo. 



Having been lately employed to analyse the ores of the olcl mines in 

 celebrated mines of Guadalcanal, in Estremadura; which, latel/rcopr-a- 

 after having been shut up for a long time, have lately been ed » furnish 

 opened again at a fresh place; I discovered in one variety p a Lna ' 

 of these ores the presence of a large quantity of platina. 

 This ore is of a gray colour, and bears considerable re- from a variety 

 semblance to that known in France by the name of gray ° gray c0 PP er 

 silver ore, the fahlerz of the Germans, [properly gray 

 copper ore.] It contains copper, lead, antimony, iron, 

 sulphur, silver, and sometimes arsenic. Its gangue most 

 commonly consists of carbonate of lime, to which are 

 added sulphate of barytes and quartz. In the month of 

 October last, I communicated this discovery to my learned 

 colleague, Mr. Fourcroy, whose knowledge and friendship 

 have been continually serviceable to me for these twenty 

 years. This fact, which appeared to ■him highly important, 

 he persuaded me to verify, by experiments so numerous 

 and varied, that they should be open to no dispute. I fol- 

 lowed his advice; and the following are the results of my 

 researches, which have left no doubt in my own mind, 

 though hitherto I have been able to operate on no con- 

 siderable quantities of ore. 



The platina appears to exist in various proportions in It kin various 

 the silver ores of Guadalcanal. Some specimens afforded Y r omVor>l\ 

 me as much as twenty marks to the hundred pounds, or ten c ?nt. to almost 

 per cent; and some exhibited merely traces of it, that not ,ng ' 

 were scarcely perceptible; which indicates, that it does 

 not form an essential, or properly constituent part of the 

 ore, and that it is simply mixed in irregular quantities in 

 various parts of the vein. The silver appears to be in The silver 

 the same case. In fact this varies greatly in its proportions, gJJJJj'JjJ, to 

 as I have found in the gray ore of Guadalcanal from four cent. 

 marks to fourteen, or from two to seven per cent of the 

 whole weight. 



The process I employed to extract the platina from these Mode in which 

 ores, after several comparative trials, consists in the fol- g d was e} 

 lowing operations. 1. After having reduced the ore to a 



fine 



