THE MINERALS OF IDAHO 161 



grown together from opposite sides of a narrow vein. Where cavities 

 occur in the specimen they are Jbounded by plane faces of quartz 

 crystals. The deposition of the owyheeite began before the quartz 

 crystals had ceased to grow, as the latter contain variously oriented 

 needles of the metallic mineral in their tips. The deposition of the 

 sulphosalt continued after the cessation of growth by the quartz 

 crystals until nearly all of the intercrystal spaces were solidly filled 

 with the owyheeite. When the quartz is broken up prismatic crystals 

 are loosened leaving lustrous molds in the owyheeite. The only 

 other minerals in the specimen are rare stains of pyrargyrite, resinous 

 yellow grains of sphalerite and small nests of sericite. 



The owyheeite is very light gray to almost silver white on fresh 

 fracture and the luster is metallic splendent. The masses are fine 

 grained and show only a faint suggestion of fibrous structure to the 

 eye. At the contact with the latest growth of quartz crystals the 

 mineral is in distinct needles penetrating the quartz. Polished 

 specimens, when examined microscopically with vertical illumination, 

 shov." every gradation from wholly massive owyheeite to material 

 made up of interlaced prismatic needles. Careful etching of the 

 polished surfaces failed to indicate the presence of more than one 

 mineral in the gray masses. In very rare and minute cavities in 

 the quartz the owyheeite occurs in prismatic needles of microscopic 

 size which are entirely too small for goniometric study. These 

 needle-like crystals are very brittle, breaking across the elongation 

 at the slightest touch in a manner indicating a well-defined cleavage 

 in this direction. Upon exposure the mineral assumes a faintly 

 yellow color. The hardness is about 2.5 and when rubbed upon 

 paper the mark is gray like hard graphite but its streak upon unglazed 

 porcelain is reddish brown. 



The blowpipe characteristics of the mineral are the usual ones for 

 sulphantimonites of lead. In the open tube it yields sulphur dioxide 

 and a copious sublimate of white antimony oxide. In the closed 

 tube fragments melt and yield a faint band having an upper ring of 

 antimony oxide succeeded downward by light rings of yellow sulphur, 

 red antimony oxysulphide, and black antimony sulphide. 



The mineral is easily soluble in hot concentrated hydrochloric 

 acid. Selected fragments of the owyheeite, separated from quartz, 

 where analyzed with the results given below: 



Analysis of owyheeite from Poorman mine 



Constituent 



Per cent 



Lead (Pb). -- 40.77 



Iron (Fe) - .40 



Copper (Cu) -- .75 



Silver (Ag) j 7.40 



Antimony (Sp) ! 30.61 



Sulphur (S) ! 20.81 



Ratios 



H). 205 0.041X5 



0. 197\ 

 .008/ 



■°m}- m - 042X2 



.255 .255 .042X6 

 .649 .649 .042X15 



54347— 26t 12 



