14 University of California Publications in Geology. [Vol. 7 



masses and stains, from the decomposition of the pyrite and 

 wolframite and former iron-bearing minerals. Dark-red earthy 

 masses with seams of brown jarosite are found in association 

 with the iodyrite. The yellowish stains of limonite color much 

 of the quartz, especially in those cavities and crevices where the 

 fibrous cacoxenite occurs. 



Manganite, Pyrolusite, Psilomelane, and Wad— The black 

 oxides of manganese are very abundant in the zone of oxidation, 

 and their close association with the several silver haloids is 

 significant of their influence in the crystallization of the latter. 

 Manganite is present in some of the pockets as long, slender, 

 vertically striated rods. Pyrolusite is finely fibrous and forms 

 coatings along the walls of some of the fissures. A felty variety 

 is seen on some of the specimens. Psilomelane is the common 

 manganese mineral of the mines. It is generally in botry- 

 oidal and small mammillary masses, and the embolite and 

 iodyrite are often deposited on them. Some of the pockets of 

 the gangue contain broken fragments of psilomelane mixed with 

 loose crystals of iodyrite. Manganese is present also in soft, 

 velvety coatings, with quite impure mixtures, and may be 

 classed as wad. Brown jarosite crystals are generally implanted 

 on such black coatings. 



Carbonates: Calcite, Manganocalcite, Siderite, Rhodochro- 

 site, Malachite, and Azurite 



Calcite. — The carbonates in the mines are all of later second- 

 ary origin. Some good calcites line the crevices near the 200- 

 foot level of the Mizpah vein. They rest upon fibrous malachite 

 and some are bright green from inclusions of the copper car- 

 bonate and some have a coating of colorless gypsum. The 

 crystals show an unusual habit. They are steep rhombohedral 

 with curved faces, and the rhombohedron is the rare negative 

 form g (0552). They are somewhat scalenohedral in habit 

 owing to the curvature of the faces, but without obtuse edges. 

 A few of the crystals have in addition the unit rhombohedron 

 /• (10T1) and the low negative rhombohedron e (01T2), both in 

 very narrow faces, as seen in figure 4, plate 1. 



