July 19, 1921 shannon: galenobismutite; 299 



The specimen was collected by Edward L. Jones, Jr., of the U. S. 

 Geological Survey and is included in an unstudied collection of ores 

 from southern Idaho. The label gives as the field number SI- 106, 

 and as the locality, Belzazzar Mine dump, Quartzburg district. The 

 specimen was collected September 15, 1915. Regarding the Belzazzar 

 Mine, Lindgren states that it is located on the Fall Creek side and has 

 been opened by sluicing and a tunnel, 200 feet below the summit. 

 Bodies of heavy sulfurets, chiefly pyrite, are exposed along the vein. 

 The western part of the vein lies in hornblende porphyrite, while the 

 eastern end has granite in the footwall and the same porphyrite in 

 the hanging wall.^ Bell gives the location of the mine as near the 

 Jerusalem Valley road, a little west of Quartzburg.^ He states that 

 the ore is merely an altered phase of the enclosing rock traversed 

 by quartz seams. The ore was free-milling on the first and second 

 levels and produced fine specimens of free gold. The third level, 

 however, showed considerable amounts of sulfides and only half of the 

 gold in this sulfide ore was recoverable by amalgamation. The ore 

 is said to average from $8.00 to $12.00 per ton. 



The specimen which contains the galenobismutite consists in the 

 main of translucent to transparent crystalline white vein quartz. The 

 sequence of deposition of the minerals is not entirely clear but there 

 is a band of more or less pure pyrite adjacent to the wall of the vein 

 and this pyrite appears to be the earliest mineral of the ore. The 

 quartz is slightly sheeted parallel to the vein wall, small grains of pyrite 

 being distributed along the partings. Pyrite occurs also in crystalline 

 grains through the quartz and also as sharply bounded cubic crystals 

 in greatly sericitized fragments of wall rock which occur in the quartz. 

 The quartz is loose textured and contains small angular cavities be- 

 tween the crystals. The galenobismutite occurs interstitially with re- 

 lation to the quartz crystals and projects as fibrous bundles of pris- 

 matic needles into the cavities. It is clearly the youngest mineral of 

 the vein, the common paragenetic position of the majority of the lead 

 sulfo-salts. 



The galenobismutite is rather light gray in color and tarnishes to a 

 yellowish color. Its luster is rather more brilliant than that of the 

 antimonial sulfo-salts of lead, and the mineral greatly resembles 

 bismuthinite in general appearance. It forms elongated prisms im- 



'Waldemar Lindgren. Mining Districts of the Idaho Basin and Boise Ridge, Idaho. 

 U. S. Geol. Survey. Ann. Rept.18, Pt. Ill: 690. 1896-97. 



* Robert N. Bell. Rept. Idaho State Inspector of Mines for 1905, p. 33. 



