NO. 2351. NOTES ON METALLIC MINERALS— SHANNON. 601 



That bismutoplagionite is strictly isomorphous with phigionite 

 and liveingite does not necessarily follow. The latter minerals are 

 of the monoclinic division of these sulphosalts, while bismutoplagio- 

 nite is probably orthorhombic. Dimorphism is very common in 

 the sulpho minerals, and it is not improbable that orthorhombic 

 forms having the compositions of plagionite and liveingite occur 

 or that a monoclinic modification of the compound 5PbS.4Bi2S3 may 

 be found. 



SILVER JAMESONITE FROM IDAHO. 



A specimen of silver ore from the Poorman Mine, Silver City dis- 

 trict, Owyhee County, Idaho, preserved in the study series of ores in 

 the United States National Museum, was found to consist in large 

 part of a light-gray metallic mineral which was not immediately 

 identifiable. Subsequent analysis indicates that this is a lead sul- 

 phantimonite similar in composition to jamesonite, but unusual in 

 containing an appreciable amount of silver. 



OCCUHEENCB. 



The mineral occurs in rather large amount in a typical rather 

 coarsely crystalline white vein quartz, which is loose textured as 

 from combs of crystals grown together from opposite sides of a nar- 

 row vein. Where cavities occur in the specimen they are bounded 

 by plane faces of quartz crystals. The deposition of the sulphanti- 

 monite began before the quartz crystals had ceased to grow, as shown 

 by the quartz crystals in some cases including variously oriented 

 needles of the metallic mineral. The deposition of the latter mineral 

 continued after the cessation of growtli by the quartz crystals, until 

 nearly all of the intercrystal spaces were solidly filled with the james- 

 onite. When the quartz is broken up, prismatic crystals are loosened, 

 leaving lustrous molds in the gray mineral. The only other minerals 

 in the specimen are rare stains of pyrargyrite, resinous yellow grains 

 of sphalerite, and small nests of sericite. 



PHYSICAL PROPERTIES. 



The sulphantimonite is somewhat unusual in appearance, being 

 quite unlike ordinary jamesonite. In color it is very light gray on 

 fresh fracture, almost silver white, and the luster is metallic splen- 

 dent. The masses are fine grained and show only a faint suggestion 

 of fibrous structure. At its contact with some of the clearer quartz 

 crystals, however, the mineral is in distinct needles penetrating the 

 quartz. Polished sections examined with vertical illumination show 

 every gradation from wholly massive material to material made up 

 of interlaced prismatic needles. Careful examination of polished 

 surfaces failed to demonstrate the presence of more than one mineral 

 in the gray masses. In very rare and small cavities in the quartz 



