160 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



PYROSTILPNITE (146) 



Silver sulphantimonite, 3Ag 2 S.Sb 2 S3. Monoclinic. 



OWYHEE COUNTY 



Pyrostilpnite, known also as fire blende, is identical with pyrar- 

 gyrite in composition but differs in crystal form. It is an exceedingly 

 rare mineral which has been identified by Penfield 44 as a single 

 crystal associated with miargyrite from the Henrietta mine, Silve 1 * 

 City district. This was fiery red in color and yielded characteristic 

 blowpipe reactions for silver, antimony, and sulphur. It was about 

 1}4 millimeters in greatest diameter and agreed exactly in habit 

 with a specimen of the corresponding arsenic compound xanthoconite 

 from Freiburg, Saxony, presented to the Brush collection by Prof. 

 A. Weisbach and with the description and figure by Miers of xantho- 

 conite from Markirch, Elsass. The faces were striated to such an 

 extent that no reliable measurements could be obtained from them. 

 While it was probably was not rare associated with the miargyrite of 

 the Henrietta mine, almost no specimens from this mine have been 

 preserved and no other specimen showing pyrostilpnite is known. 



XANTHOCONITE (146a) 



Silver sulpharsenite, 3Ag->S.As 2 S 3 . Monoclinic. 



OWYHEE COUNTY 



The rare silver mineral xanthoconite is identical with proustite in 

 composition but differs in crystallization and is usually yellow to 

 orange-red or brown in color. It is reported to have occurred in the 

 rich ores of the Flint district associated with polybasite and steph- 

 anite. 45 None of the mineral was recognized in the few specimens 

 of the rich ores from this district which have been available for 

 examination. Browne was a Freiberg man, familiar with silver 

 minerals, and his identification is probably to be relied upon. 



OWYHEEITE 



Lead silver sulphantimonite, 8PbS.2Ag 2 S.5Sb 2 S 3 . Orthorhombic. 



OWYHEE COUNTY 



A mineral making up a considerable portion of a specimen of 

 silver ore from the Poorman lode, Silver City district, was described 

 as a silver bearing variety of jamesonite 45a and later was given the 

 name owyheeite, it being evident that it was a distinct species. 46 

 The mineral occurs in rather large amount in a typical rather coarsely 

 crystalline white vein quartz which is loose textured as from combs 



** S. L. Penfield, quoted by Lindgren. U. S. Geol. Survey, 20th Ann. Rept. pt. 3, p. 169, 1900. 

 « J. Ross Browne. Mineral Resources of United States, 1868, p. 528. 

 «° Earl V. Shannon. Proc. U. S. Nat. Mus., vol. 58, pp. 601-604, 1920. 

 * 6 Earl V. Shannon. American Mineralogist, vol. 6, pp. 82-83, 1921. 



