1912] EaMe : The Minerals of Tonopah, Nevada 



9 



and the brachypinacoid b (010). A few crystals had in addition 

 the form r (112), and one showed a good face of a new form 

 o (443). The typical habit of the crystals is seen in figure 1, 

 plate 1. 



Measured Calculated 



(110) 



(1T0) 



, 60°08' 



60°10' 



(110) 



(010) 



30 00 



29 55 



(001) 



(111) 



61 15 



61 14 



(001) 



(112) 



42 14 



42 19 



(001) 



(443) 



67 46 



67 38 



Stephanite. — "Whether stephanite is mixed with the polybasite 

 in the black silver bands is practically impossible to determine. 

 All of the crystals of the brittle black silver occurring in the 

 cavities of the specimens examined are polybasite, so the pres- 

 ence of stephanite was not proved. 



Pyrargyrite. — The dark ruby silver is generally found as a 

 fissure-filling in the quartz, often intergrown with argentite and 

 polybasite, and accompanied by wires of native silver. Most of 

 the mineral appears granular in the quartz, in the characteristic 

 dark gray bands with reddish cast. Small dark-red crystals have 

 been formed in some of the cavities, consisting of the simple com- 

 bination of second order prism a (1120), base c(0001), and 

 rhombohedron r ( 1011 ) . 



Measured Calculated 



(2TT0) : (1120) 60°02' 60°00' 



(0001) : (lOTl) 42 18 42 28 



Tetrahedrite. — Thick tabular plates of tetrahedrite in the 

 gangue of quartz and feldspar, with wires of native silver, occur 

 in a specimen from the Belmont mine. 



Haloids : Cerargerite, Embolite, and Iodyrite 



Cerargerite. — The chloride of silver is the most abundant 

 member of the haloids in the deposits. It occurs throughout the 

 zone of oxidation, but is principally found in the upper portion 

 of the zone. Waxy coatings of the mineral cover several square 

 feet in area and minute crystals are abundantly disseminated in 

 the soft kaolinized feldspar, and in the small cavities of the 

 quartz. The coatings and crystals have a very brilliant adaman- 

 tine to waxy luster, and most are of a translucent pale gray color. 



