288 MINERALOGY 



alluvial deposits of the Ural Mountains, Russia, in 1822. Here 

 nuggets weighing as much as 18 kilos were found. The largest, 

 weighing 18.57 kilos, is in the Demidoff collection of minerals at 

 St. Petersburg. The larger part of the world's supply of the present 

 day, about 15,000 pounds annually, is derived from the Russian de- 

 posits. A peculiar black sand left with the gold in the washings of 

 the Pacific slope, particularly in British Columbia and the states of 

 Oregon and Washington, contains small amounts of platinum; from 

 this source a few ounces are obtained annually. Platinum has been 

 reported as contained in, serpentine of the Urals ; in a pegmatite of 

 Copper Mountain, British Columbia; in a decomposed schist of 

 Broken Hill, Australia; in limonite nodules in Mexico; in an altered 

 limestone of Sumatra. In addition it is connected with certain sul- 

 phides, as the pyrrhotite of Sudbury, Canada ; covellite in Wyo- 

 ming; and chalcopyrite of the Key West mine near Bunkerville, 

 Nevada, where it is associated with nickel, , as at the Sudbury 

 locality. Possibly in these associations platinum may be in the 

 form of arsenide, as sperrylite has been reported from both Sud- 

 bury and the British Columbia localities, but has not as yet been 

 reported from Nevada. 



Owing to the high fusing point and its insolubility in single acids, 

 platinum crucibles are used in chemical analyses. It is also used 

 in thermoelectric couples for the measurement of high tempera- 

 tures ; as a catalyzer to oxidize SO 2 to S0 3 in sulphuric acid works. 

 Having the same coefficient of expansion as glass, it is used to carry 

 the electric current through the glass walls of physical apparatus. 

 There are many other minors uses ; and since the supply cannot 

 keep pace with the demand, the price is constantly increasing, until 

 at the present time platinum is more than double the value of gold. 



COPPER 



Copper. Native Copper, Cu; Isometric; Type, Ditesseral 

 Central ; Common forms, a (001), o (111), d (101), h (410) ; Twin- 

 ning plane, 111 ; Malleable, ductile; Fracture, hackly ; H. = 2.5-3 ; 

 G. = 8.8-8.9; Color, copper red; Streak, shining; Metallic; 

 Opaque. 



B.B. Easily fusible (1084). In the blue cone of the O. F. 

 yields a green flame. On coal becomes black after fusion from the 

 formation of black oxide. Dissolves in HN0 3 or HC1, yielding a 

 solution which becomes intensely blue on the addition of an excess 

 of ammonia. 



