Genth and Penfield — Contributions to Mineralogy. 187 



72° 21', average 72° 41', calculated for 830 ^ 010 = 72° 35f, 

 while for 310 ^ 010 the calculated angle is 74° 26'. The crys- 

 tals are usually terminated by t, or by t and a pyramid A, H2, 

 in the zone t, b The dome t was either dull or had a sort of 

 undulatory surface, so that it gave no distinct reflection. The 

 pyramid A gave only faint reflections and yielded the following 

 measurements. 



Measured. Calculated. 



A a b, 112 a 010 = 68° 51' and 69° 20' 69° 4f 



Z/ a £, 112 ^ §30 = 108° 28' 108° 14 



Only the thinnest cleavage splinters of this material were 

 at all transparent, so that no attempt was made to study the 

 optical properties. 



Color iron black to brownish black, luster submetallic, in- 

 clining to adamantine. Powder greenish gray. Sp. Gr. = 

 7-163-7-091. 



The analysis gave, after deducting 0*34 per cent of quartz : 



I. Lincoln Co., N". M. (GTenth.) II. Mammoth Dist., Nevada. 



WO, 76-33 74-88 



FeO"._ 3-82— 3-98 0-56 



MnO. 19-72 — 20-08 23-87 



CaO .. 0-13 0-14 



MgO ...trace I Cu0 0-08 



100-00 99-61 



d. From Monmouth District, Nye Co., Nevada. 



For comparison we have examined the hiibnerite from 

 Riotte's original locality. The specimens at our disposal 

 showed no distinct crystals but only cleavage masses, implanted 

 on quartz. Color brownish black to iron-black, powder green- 

 ish-gray. A little of the manganese is higher oxydized, as the 

 mineral evolved some chlorine, when treated with hydrochloric 

 acid. The analysis is given under II above 



2. Hessite from Mexico. 



Prof. Carlos F. de Landero of Guadalajara kindly presented 

 a specimen of hessite from a recent occurrence at the Refugio 

 Mine, San Sebastian District, State of Jalisco, Mexico, which 

 was analyzed by Mr. Jas. S. de Benneville. It is granular, of 

 a dark lead gray color, and so very largely and intimately 

 intermixed with quartz, that no pure material could be picked 

 out for analysis. The composition of the mixture was found 

 to be 



