Dr. Genth’s Contributions to Mineralogy. 83 
y own and Wehrle’s analyses speak decidedly in favor of the 
latter formula, and even Berzelius’s analysis shows but a slight 
difference in respect to bismuth and sulphur. 
he composition of tetradymite therefore appears to be 
Bi (Te, S)s; but it cannot be regarded as a settled question, since 
we have only a few analyses of this rare substance which allow 
of a fair calculation. Jackson’s analysis is deficient either in 
sulphur or in tellurium, and the 60-31 p.c. of bismuth require 
1:23 p.c. of sulphur (or an equivalent quantity of telluriam) 
more than he found, in order to have 3 equivalents of the electro- 
negative elements in combination with one of bismuth. In 
acid quite distinctly, and judging from the intensity of the horse- 
radish odor, there cannot be a large quantity of selenium in the 
mineral. 
Dr. Jackson remarks, that he observed impressions of the edges 
of crystals of tetradymite in metallic gold. I have in my cabin 
a magnificent specimen of native gold from Whitehall, ich 
appears to be a pseudomorph of tetradymite. TI intend making a 
thorough J amsraeennig of it and will describe it as soon as I find 
leisure to do s 
2. Gray eee (probably a new mineral*).—At McMackin’s 
mine, vain County, N. C., I found a mineral associated with 
carbonate of magnesia, talc, blende, iron pyrites and galena, 
which is closely allied to some argentiferous gray coppers. As 
no locality in the United States of a similar mineral has yet been 
made known, an examination of it, I thought, might give inter- 
esting results. 
assive, apparently without any crystalline structure: H.=4°5; 
sp. gr.? —; color nearly iron black, subtranslucent, when in very 
thin splinters with cherry-red color ; streak brownish-red ; lustre 
submetallic ; fracture conchoidal ; brittle. 
B.B. on charcoal it fuses readily =1, makes incrustations of 
antimony and zinc, and gives off the odor of arsenic and sulphu- 
rous acid; with carbonate of soda on charcoal yields a globule of 
silver and copper. Soluble in nitrohydrochloric acid with sepa- 
ration of chlorid of silver. 
0-1330 grs. were dissolved in nitrohydrochloric acid, the liquid 
diluted with a large quantity of water, and the chlorid of ned 
filtered off. It gave 0-0140 grs. silver. The filtrate was alm 
evaporated to dryness, the arsenic acid reduced by bisulphite “of 
ammonia, the excess of the latter decomposed by hydrochloric 
acid, and copper, arsenic and antimony precipitated by hydrosul- 
phuric acid. ‘The precipitated sulphids were filtered and treated 
* Read before the Acad. of Nat. Sci. of Philad., Feb. 15, 1853. 
