314 G. J. Brush—American Sulpho-Selenides of Mercury. 
ye eae bead; with soda on platinum uh at imparts to the 
e pale green color characteristic of sodium manganate. 
Chemical composition.—The quantitative sratuihation of the 
mineral was made by Mr. W. J. Comstock, assistant in the 
Sheffield Laboratory. He followed he ethod of H. Rose, 
precipitated a havi aionde This precipitate was care- 
fully tested aud found to be entirely free from selenium. An 
examination was also made to ascertain if anything besides 
- T: IL. Ill. IV. Mean. Ratio. 
Seloninm .2. 0)... ce 4°69 4:47 4-58 “058 3 423 
COL SCPE SPEER ES Son coe et Oa bee EPs ees 
oa Ce ee 81°73 82°12 81:93 
PIO eS 0°61 =: 0°48 0°54 eid 429 
Manganese _______. 0-68 0-70 ; 0-69 © 012 
r 99°42 
These figures prove the mineral to be gj Hg(S, Se), 
or a mercuric sulpho-selenide, in which the ratio of the sulphur 
to the selenium is about 6:1. This Pengbee it under the 
mineral species gs am which H. Rose found to be a mercuric 
sulpho-selenide, with the ratio of S to Se of 4:1, a relation 
which Rose tives considered unimportant, for he remarks 
that mercurie selenide a 
complete correspondence in physical characters, and Dr. 
berry’s discovery of a considerable quantity of this rare species 
at a new locality is an interesting fact for mineralogical science. ° 
In this connection it may not be amiss to review the occur- 
* Poggendorff’s Ann., xlvi, 318. 
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