88 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



labeled as from " Coeur d'Alene, Kootenai County, Idaho," is doubt- 

 less from some mine in the Coeur d'Alene district. These are very 

 rich, consisting entirely of native silver in curved columns and wires 

 on masses of crystallized argentite which forms spongy masses. The 

 crystals of silver sulphide are distinctly orthorhombic in appearance 

 and were thought to be acanthite. Careful measurement of a num- 

 ber of them, however, indicated that the angles were not those of 

 acanthite but that the prismatic and tabular forms were elongated 

 and distorted dodecahedrons with various modifying faces. Four 

 different habits are shown in Figures 2 to 5. These crystals, upon 

 measurement, gave the following angles : 



Measurement of argentite from the Coeur d'Alenes 



Quality, description 



Poor, dull 



Very good, excellent 



Medium 



Very poor. 



Medium 



Measured 



31 



45 00 



44 



18 59 



30 10 



90 00 



90 00 



44 15 



90 00 



70 41 



Calculated 



00 



45 00 



00 



18 26 



30 58 



90 00 



90 00 



45 00 



90 00 



71 04 



PETZITE 



Telluride of silver and gold, (Ag, Au)jTe. 



(44) 



Massive. 



IDAHO COUNTY 



Petzite has been reported to occur in the Black Diamond mine 

 in the Dixie district in a streak of ore 18 inches (50 centimeters) wide 

 from which assays of several hundred dollars in gold were obtained. 

 The identification of the mineral has not been confirmed. 



GALENA (45) 



LEAD GLANCE 



Lead sulphide, PbS. . Isometric. 



Galena is a mineral found in Idaho in greater or less amount in 

 practically every mining district and in all classes of mineral deposits. 

 It is the essential primary mineral of the lead-silver ores, the most 

 important of which are those in the Coeur d'Alene district in Shoshone 

 County and in the Wood River district in Blaine County, although 

 valuable individual lead mines are operated in Custer, Lemhi, and 

 other counties. Less abundantly this mineral occurs throughout the 

 State as an accessory constituent of gold, silver, and copper ores. In 

 the silver and lead-silver deposits the galena commonly contains more 

 or less silver while in gold veins it is usually gold bearing. Well 

 crystallized specimens are not known from any locality of the State, 

 euhedral crystals being exceedingly rare and of small size. The 

 following discussion, while not exhaustive, mentions the principal 

 known localities and occurrences. 



