1835.] Improvements in Science. 275 



from Cornwall, consists, according to Trolle Wachtmeister, 

 of 



100-26 

 28. Platinum, in Siberia, is found in fine sand. A piece 

 was obtained at Nischne Tagil, weighing 4 Kilogrammes, 

 (8 lbs. 13 oz. 4 dr. avoird.) in 1827, and three bits in 1831-32, 

 the two first weighing 8 kil. (17 lbs. 11 oz.) and the third 

 5 kils. (11 lbs. 1 oz. 1 dr.) It is accompanied with gold, 

 osmium, iridium, magnetic iron, chromium, brown oxide of 

 iron, oxide of titanium, epidote garnet, rock crystal, and 

 sometimes diamonds. The sand is composed of jasper, 

 quartz, and greenstone, and likewise small yellow crystals 

 of rhomboidal, dodecahedrons, resembling chrysoberyl, the 

 nature of which is not known. Among the rocks which 

 accompany platinum in the Uralians, serpentine is the most 

 remarkable. Gold appears generally to exist in the same 

 rock with platinum. (Journ. de St. Petersburg, 1833.) 

 " 29. Osmium and Iridium. — Two minerals have been ob- 

 tained in the Uralians, composed of these two metals. One 

 found at Newiansk possesses a compound crystalline form, 

 consisting of the combination of a double pyramid with six 

 faces, with a right hexagonal prism. It possesses a blue 

 metallic lustre. Hardness nearly that of quartz. Sp. gr. 

 19-386—19-471. Before the blowpipe, on charcoal, it does 

 not decompose. In the matrass with saltpetre a feeble 

 smell of osmium is observable. It is found in the auriferous 

 sand of Newiansk, 95 versts to the north of Katharinenberg. 

 It is also observed at Bilimbajewsk and Kyschtim, and 

 several other places in the Urals. The crystals of the 

 variety from Nischne Tagil have the same form as the 

 preceding. The colour is blueish-gray, analogous to that 

 of sulphuret of antimony. Hardness about that of quartz. 

 Sp. gr. 21*118. Before the blowpipe, on charcoal, becomes 

 black, and loses its lustre, and disengages a pungent smell 



t2 



