68 H L. Wells — Sperrylite, a new Mineral. 



pyrrhotite and some silicates could be seen. ' In order to purif j 

 the substance it was treated for a short time with warm aqua 

 regia to remove sulphides, etc.; then it was treated for a long time 

 with hot hydrofluoric acid to remove the silicates. After 

 these treatments the sand possessed great brilliancy, but it was 

 found by microscopic examination to contain some transparent 

 grains which on chemical examination proved to be stannic 

 oxide. Prof. S. L. Penfield kindly examined these grains and 

 found that they corresponded perfectly in their optical proper- 

 ties with cassiterite. 



Nearly all the grains of the new mineral showed extremely 

 brilliant crystal-faces, though most of the crystals were frag- 

 mentary ; in size they were mostly between *05 and '5 mm (-g^-g- 

 and -^q- inch) in diameter. 



The color of the mineral is nearly tin white or about the 

 same as that of metallic platinum ; the fine powder is black. 



The specific gravity taken twice on the same 8 grams of mate- 

 rial, was 1O420 and 1 0*42i at 20° ; this material was the same 

 that was used for analysis, and, correcting the average of these 

 results for 4'62 per cent of cassiterite, the true specific gravity 

 becomes 1O602. 



The sand is not easily wet by water and shows a marked 

 tendency to float when brought to its surface. By placing a 

 shallow layer of water upon the mineral in a vessel it is easy 

 to nearly cover the surface of the water with a continuous 

 layer of the crystals by inclining the vessel repeatedly so that 

 they are brought to the surface. This phenomenon is not due 

 to any oily substance upon the particles, for they float with 

 equal readiness after being boiled with a strong solution of pot- 

 ash and washed with alcohol and ether. When they are float- 

 ing upon water it is quite difficult to cause them to sink, and 

 when carried to the bottom by a stream of water they fre- 

 quently carry down small bubbles of air which they completely 

 surround and hold down by their weight. If ether is poured 

 upon water on which they are floating, they remain suspended 

 between the two liquids, and, by agitation, can frequently be 

 made to sink to the bottom in spherical clusters surrounding 

 globules of ether. 



The mineral is only slightly attacked by aqua regia; even 

 when it is very finely pulverized and the strongest aqua regia 

 is repeatedly applied with the aid of heat for several days, the 

 solution is only partial. 



Pyrognostics — The mineral decrepitates slightly when 

 heated. In the closed tube it remains unchanged at the fusing- 

 point of glass. In the open tube it gives very readily a subli- 

 mate of arsenic trioxide and does-»not fuse if slowly roasted, but 

 if rapidly heated it melts very easily after losing a part of the 

 arsenic. Perhaps its most characteristic reaction is the follow- 



