150 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



Considering the character of the crystals the measurements recorded 

 in the following table approximate as closely as can be expected to the 

 values derived from the fundamental measurements of Lewis given 

 in Dana's mineralogy. 



Measurement of miargyrite from Henrietta mine 



Angle 



Measured Calculated 



c(001) A o(100). 



c(001) A m(101) . 

 c(001) A o(101).. 

 a(100) A <(111)-. 



*(111) A s(211)-. 



98 00 



98 09 



98 16 



40 15 



48 07 



69 25 



98 37 



41 24 



48 21 



69 45 



14 17 



When roasted before the blowpipe on charcoal the mineral gives a 

 coating of oxide of antimony and a globule of silver results from long 

 continued heating. 



Several specimens of ore from the Henrietta mine, which are pre- 

 served in the National Museum all show some crystals of miargytire. 

 and a specimen of this mineral in the University of California mineral 

 collection is labeled as from the Rising Star mine, which is in the 

 Flint district. This last specimen was examined optically by 

 Larsen 25a who found it to be optically positive with 2V moderate; 

 nearly opaque and with the lowest refractive index (a) greater than 2.72. 



DUFRENOYSITE (126) 

 Lead sulpharsenite, 2PbS.As2S3. 



Orthorhombic. 



BLAINE COUNTY 



Dufrenoysite is reported to occur in the Wood River district in 

 considerable quantity with ores of lead. 26 No specimens have been 

 seen by the writer. 



BOISE COUNTY 



This mineral is also reported to occur in the Crown Point vein in 

 the Banner district. 28 Very few specimens of the rich ores of this 

 vein have been preserved and none showing dufrenoysite have been 

 available for examination. 



»« Esper S. Larsen. U. S. Geol. Survey, Bull. 679, p. 110, 1921. 



26 Albert Williams, jr. Useful Minerals of the United States in U. S. Geol. Survey Mineral Resources- 

 for United States., 1887, p. 723, copied in U. S. Geol. Survey Bull. 624, p. 117, where the latter locality has 

 apparently erroneously been changed to read Bonner County. 



