1885.] **1 [Genth. 



Tin. — The tin exists in the form of irregular, somewhat globular grains 

 or aggregations of such grains; they are distinctly crystalline, from 0.1 to 

 rarely over l mm in size. When magnified 60 diameters they appear to be of 

 an uneven surface, showing planes which are too indistinct, however, for 

 determining their form. They are grayish-white and of metallic lustre. It 

 was impossible to select enough of the pure grains to determine their 

 specific gravity or to make a quantitative analysis. A portion, treated 

 with hydrochloric acid, dissolved readily with disengagement of hydro- 

 gen, leaving fine scales of iridosmine behind. Not a trace of any other 

 metal but tin could be found in the solution. 



Platinum. — The sample from the Aberfoil river yielded only a very mi- 

 nute quantity of platinum, when the portion insoluble in hydrochloric 

 acid was treated with aqua regia, whilst that from the Sam river contained 

 a considerable amount of this metal. 



The grains of platinum are of irregular shape, mostly flattened. Aqua 

 regia dissolves some of the grains very slowly, leaving a crystalline skele- 

 ton of very fine scales, probably of iridosmine. Other grains are hardly 

 acted upon and are probably iridium or platin-iridium. The solution con- 

 tained principally platinum, but also iridium and palladium. 



Iridosmine. — The so-called iridosmine seems to be present, both as new- 

 janskite in tin white, flat scales and as sisserskite in grayish- white or lead- 

 colored scales. Some of the scales are indistinct hexagonal plates, but 

 mostly have an irregular shape. 



Gold. — The gold which I have observed in these washings is associated 

 with quartz and of a deep yellow color, showing its high degree of fine- 

 ness. 



Copper. — The Sam river washings contain fine particles of native copper 

 in the wire form. 



Cassiterite. — I have observed this mineral more largely in the Aberfoil 

 river sample ; it is mostly in small, rounded grains, the largest about 10 mm 

 in size; some are of a deep aurora red color, others are hyacinth red, red- 

 dish-brown or variegated, black, red and white ; crystals could not be ob- 

 served. 



Corundum. — Sapphires in rounded grains, also in asteriated crystals, the 

 largest 12 mm in diameter, and of a deep blue color occur most abundantly 

 in the washings of the Aberfoil river, but also, with other varieties of co- 

 rundum, in those of the Sam river. 



Besides these and an abundance of quartz I have observed topaz of a 

 yellowish-white color, orthoclase, garnet, brown tourmaline and other 

 minerals, too small to distinguish. 



2. Joseite and Tetradymite. 



The peculiar telluride of bismuth from San Jose\ Minas Geraes, Brazil 

 (DufrSnoy's bornine, which afterwards was named joseite by Kenngott), 

 was analyzed by Damour in 1845. The composition being so peculiar, 



