186 Genth and Pen field — Contributions to Mineralogy. 



Some groups of radiating crystals of a brownish yellow color, 

 not over 2 mm in diameter have been noticed, which probably 

 are also hiibnerite. 



An analysis of the radiated variety of a brownish black color, 

 yielding a pale grayish brown powder, and having the specific 

 gravity 6"713 gave, after deducting 8*608 per cent quartz: 



W0 3 74-75 



FeO 2-91 



MnO 21-93 



CaO 0-11 



MffO trace. 



99-70 



b. From Cement Creek on Bonita Mountain near Silverton, 

 San Juan Co., Colorado. 



This variety we have not been able to obtain in isolated 

 crystals. It is associated with quartz and pyrite and occurs in 

 a radiating and divergent mass, up to 40 to 50 mm in length, with 

 distinct clino-pinacoid cleavage. Color hair-brown to reddish 

 and yellowish brown, in thin splinters transparent, luster sub- 

 metallic, inclined to silky. The fine powder is of isabella 

 color. Sp. gr. = 6'891. 



The analysis gave, after deducting 2 '4 per cent of quartz : 



Harry F. Keller* 



WO, 76-63 76-14 



FeO 1-61 —1-63 211 



MnO 21-78 21-63 



CaO 0-09 0-12 



Mo'O trace trace 



100-11 100-00 



Sp. gr.= 6-780 



c. From Bonito Mountain near White Oakes, Lincoln Co., 

 1ST. M. 



This variety occurs in fissures in granite. The crystals are 

 long prismatic and for the most part coated with drusy quartz. 

 The prismatic faces are usually vertically striated, but a few 

 crystals were found which gave very good reflections. In the 

 prismatic zone b, m and q, were observed, but q, which is new, 

 was the most prominent. The symbol 830. i-|, approximates 

 to 310, i-S, which has been observed on wolframite, but four 

 independent measurements, where the reflection from q were 

 sharp and distinct, gave q a b = 72° 55' ; 72° 46' ; 72° 41' and 



* After deducting 2-13 per cent of quartz, the analysis of Harry F. Keller of the 

 same variety (megabasite from Bonita Mountain near Silverton, Col., in Franklin 

 Institute Journal, August, 1889), gave the above composition. 



