BENJAMINITE, A NEW SULPHOSALT MINERAL OF THE 

 KLAPROTHOLITE GROUP. 



By Earl V. Shannon, 



Assistant Curator, Department of Geology, United States National Museum. 



INTRODUCTION. 



The present description pertains to a mineral from near Round 

 Mountain, Nye County, Nev., which occurs in a quartz vein with 

 molybdenite, mica, and minor amounts of other minerals. Upon 

 analysis this has been found to be an argentiferous sulphobismuthite 

 of lead and copper differing in ratios from any known mineral. For 

 this new mineral the name proposed is benjaminite, in honor of 

 Dr. Marcus Benjamin of the United States National Museum. 



The specimens first examined v/ere sent to the United States 

 Geological Survey some years ago, where they were incorporated 

 in a series of bismuth ores by Frank L. Hess and forwarded to the 

 National Museum. It was not known who sent them in and the 

 only information regarding them was contained in a label reading 

 "Aikinite Mining Co., Round Mountain, Nevada." It was con- 

 cluded from the name of the mining company that the mineral had 

 been identified as aikinite and that it Avas a characteristic mineral 

 of the deposit. Nothing further could be learned about the mineral 

 or the mine, however, until an inquiry was addressed to H. G. Clinton, 

 of Manhattan, Nev. Fortunately Mr. Clinton was familiar with the 

 mine, its geology, history, and mineralogy, and was able to visit the 

 locality and to supply an additional very fine specimen of the benja- 

 minite, especially welcome since the original small lot had been 

 almost entirely used up in the several analyses, as well as specimens 

 of the associated minerals. It developed from this correspondence 

 that the material originally received at the Geological Survey had 

 also come from Mi\ Clinton. The writer takes this opportunity to 

 acknowledge his obligation to Mr. Clinton for his generosity and his 

 thorough knowledge of the region. The following is quoted from 

 his letter: 



The Aikinite Mining Co. has been out of existence for 3'ears but they were 

 operating the Outlaw Mine some 12 miles north of here [Manhattan] at the head 

 of Mariposa Canyon. 



The mineral [benjaminite] occurs in large and small bunches and blotches in 

 a dense white quartz, near the southern contact of a rock locally called pegmatite, 

 but described by J. M. Hill as a soda-granite, and an intrusive rhyolite. I have 



No. 2537 — Proceedings U. S. National Museum, Vol. 65, Art. 24. 



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