294 J. W. Mallet—Selenide of Bismuth from Guanajuato. 
Art. XLIV.—On the chemical composition of Guanajuatite, or Sel- 
entde of Bismuth, from Guanajuato, Mexico; by J. W. MALLET, 
University of Virginia. 
THIS mineral seems to have been first noticed by Sefior Cas- 
tillo in March, 1878, and was by him partially described* as 
a sulpho-selenide of bismuth. 
In the Guanajuato journal ‘La Republica” for July 18, 
1873, Fernandez t published a full description, giving to the 
mineral the name Guanajuatite, and stating that it is solely a 
selenide of bismuth, a small amount of sulphur found being 
attributed to admixture with a little pyrite. In the same year 
or 1874 Rammelsbergt obtained as the result of a partial exam- 
imation on a very small quantity, 
EEE EES ae Se OE 16°7 
ee Oak 
82°1 
and suggested the Phase of zinc. The mineral was more 
fully examined by Frenzel,§ whose analysis yielded, 
mencere ss 24°13 
Rupee oe. Se es - 6°60 
Wiemuth e250. ey ee 67°38 
98°11 
whence the formula has been deduced—2Bi,Se, . Bi,S,. 
In the 2d Appendix to the 5th edition of Dana’s Mineral- 
ogy | the name Frenzelite was proposed for the species, but 
this has subsequently been retracted | in favor of the prior 
claim of the name Guanajuatite given by Fernandez. 
The above are up to this time, I believe, the only published 
notices of the mineral in question. They leave two doubts in 
regard to its composition, namely, whether sulphur is really a 
constituent or only found from accidental admixture, an 
whether zinc is present or not. 
At the Bascessedl pres Exhibition of 1876, my friend Sefior 
. 
the Mexican Commission, was kind enough 
* Naturaleza, ii, 174 (1873); Jahrb. Min. (1874), 225, 
in this Journal, April, 1877, p. 
Mine! 
, p- 319. 
p App. to 5th ed. Dana’s Mineralogy (March, 1875), p. 22. 
Loe. cit. 
Min. (1874), 679. 
{ This Journal, loc. cit. 
