63 



lite was first found at the Vermilion mine in the gossan or loose 

 material, and was named after Mr. Francis L. Sperry of the C. C. C by 

 Messrs. Horace L. Wells and S. L. Penfield, of the Shefifield Scientific 

 School, who examined and described this new species. It is isometric ; 

 simple cubes are common, octahedrons are exceptional, while the 

 majority of the crystals are combinations of the cube and octahe- 

 dron. H. — Between six and seven, as it scratches felspar but not 

 quartz. The crystals have no distinct cleavage, but are very brittle and 

 break with an irregular, probably conchoidal fracture. The chemical 

 composition, according to the mean of two analyses was as follows : — 



Arsenic 40.98 



Antimony 50 



Platinum.. 52-57 



Rhodium 72 



Palladium trace. 



Cassiterite or oxide of tin 4.62 



The composition is therefore represented by the formula Pt A&„., 

 a small portion of the platinum being replaced respectively by rhodium 

 and antimony. The color of the mineral was nearly tin white or about 

 the same as metallic platinum. The fine powder is black. Nearly all 

 the grains showed extremely brilliant crystal laces, though most of the 

 crystals were fragmentary in size they were usually J^ — 5 w^h of an inch 

 in diameter. Sp. Gr. 10.602. 



ROASTING. 



The metallurgical treatment of this ore commences at the roast 

 yard whither it is conveyed, and, being piled in convenient heaps on 

 previously laid cordwood, is exposed at high temperatures without 

 fusion, or, at most, incipient fusion, to the action of a current of air. 

 The objects of this roasting are, ist, an oxidation of the iron, and, 

 incidentally, of the sulphur, as complete as is possible without involving 

 an undue loss of copper in the slags of the following smelting, and 2nd, 

 the expulsion of arsenic if there is any present. If the oxidation be 

 very imperfect the resulting matte will contain so much iron that 

 its bringing forward will be unduly costly, while, if the oxidation be too 

 thorough, an undue loss of metal will occur on smelting the roasted ore. 



