398 Scientific Intelligence. 



Palladium -gold, an alloy of the two metals in varying propor- 

 tions, is not uncommon and the scales of " white gold " belong- 

 ing here were noted as early as 1700 though at first supposed to 

 be silver. 



It occurs in the gold washings at various points in the states 

 Goyaz and Minas Geraes. It is also found, with native platinum 

 in the rock itself, thus in the " Jacutinga " at the Gongo Socco 

 mine near Caethe Minas, at Itabira do Matto Dentro and at Maquine 

 near Villa Marianna. It also occurs at Candonga, Minas Geraes, 

 in a pyroxene rock which is probably derived from a limestone by 

 contact metamorphism. This rock forms layers in the itabirite. 



Platinum has been known to exist in Brazil for about one hun- 

 dred years, but, previous to the identification of palladium, it 

 was often confounded with the alloy palladium-gold. The explo- 

 rations and investigations of the past thirty years have added 

 largely to the number of localities of native platinum, which may 

 be summarized as follows : 



(a) It occurs sparsely disseminated through the highly aurif- 

 erous Jacutinga, interbedded in the itabirite, as at Gongo Socco. 



(b) In the auriferous quartz veins of the crystalline schists on 

 the Rio Bruscus, Pernambuco. 



(c) Associated with the less frequent diamond and probably 

 derived from quartz conglomerates, on the east slopes of the 

 Serra do Espinhaco from Itambe do Matto Dentro to Itambe do 

 Serro. 



(d) In the Rio Abaete and its left tributaries, here probably 

 derived from olivine-rocks as in the Urals. 



It is noteworthy that the platinum of occurrences (c) and (d) 

 varies widely in composition ; that of Conceicao is non-magnetic 

 and free from palladium with a specific gravity of 20*5 ; that 

 from Condado is non-magnetic and rich in palladium, and that of 

 Abaete is strongly magnetic and free from palladium, but rich in 

 iron. The specific gravity of the platinum from Condado is 

 from 15 to 15*5. The specific gravity of the metal from Abaete 

 could not be determined because it was impossible to obtain the 

 fine powder free from gold and perovskite. 



In the occurrences (a), (b) and (d) the platinum seems to be a 

 primary constituent, but in the remaining case, where it accom- 

 panies the diamond, it has so peculiar a form that a secondary 

 formation is thought probable. Here the platinum appears not 

 as rolled grains but in hollow forms, sometimes fern-shaped, with 

 thin walls and mammillary or botryoidal, non-crystalline, surface; 

 the structure is both concentric and fibrous. These forms are so 

 unusual that a possible secondary origin is suggested, perhaps a 

 deposit from solutions derived from the decomposition of sul- 

 phides carrying platinum. Such a formation the author regards 

 as quite possible, since in the United States and Norway, ores of 

 this kind (pyrrhotite, covellite, chalcopyrite) have been shown to 

 carry platinum and to be associated with sperrylite (PtAsJ. 



6. Platinum Resources in the United States. — The Geological 

 Survey has undertaken the investigation of the resources of plati- 



