392 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



from this mine consist of garnet rock containing chrysocolla, fluorite, 

 and copper pitch ore. The green chrysocolla grades into a pale 

 bluish-green soft material of faint silky luster. Under the microscope 

 this shows a finely foliated crystalline structure with moderate bi- 

 refringence. The fibers have parallel extinction with positive 

 elongation. The color in transmitted light is brownish-green in the 

 aggregated fibers with no noticeable pleochroism. The mean 

 refractive index is about 1.615. 



Specimens from the Peterson lease contain masses of sky-blue 

 chrysocolla up to 2 cm. in diameter embedded in ferruginous clayey 

 material. The chrysocolla has a radiated structure as though 

 pseudomorphous after malachite. 



Specimens from the Copper Bullion tunnel consist of large masses of 

 fairly pure corneous to vitreous blue-green chrysocolla. The chrys- 

 ocolla has a botryoidal surface where lining small cavities which 

 contain a little copper pitch and malachite. 



A bluish-green mass occurring in nuorite from the Empire mine is 

 soft and waxy in appearance and resembles some serpentines. Under 

 the microscope this is finely scaly in structure and entirely crystalline 

 with medium low birefringence. It is biaxial positive with 2V near 

 0°. The refractive index averages about 1.583 but varies to 1.595. 

 The mineral is easily soluble in cold 1 : 1 hydrochloric acid and the 

 solution contains much copper with no iron, lime, nickel or magnesia. 

 Associated with this is a yellow-green mineral which, under the 

 microscope, appears as radial fibrous spherulites of greenish-yellow 

 color and no notable pleochroism. The extinction is parallel, 

 elongation positive, refractive index above 1.59. 



Umpleby noted the crystalline character of the green chrysocolla 

 from the Mackay mines and described it. 3 Under the microscope 

 the material appears as acicular crystals with both parallel and radial 

 disposition and as irregular grains and mammillary crusts. The 

 mineral is uniaxial and optically positive with positive elongation and 

 high birefringence. The indices of refraction, which are slightly 

 variable, are co = 1.46, e= 1.54. The material is distinctly pleochroic 

 with oo = colorless and e = pale bluish-green. It is hexagonal or 

 tetragonal in crystallization with hardness about 3 and density 2.4. 

 The luster is vitreous, color pale bluish-green, streak white; brittle. 

 An analysis of the purest sample of this chrysocolla which could be 

 selected yielded the following results : 



•J. B. Umpleby. Crystallized chrysocolla from Mackay, Idaho. Journ. Wash. Acad. Sci., vol. 4, 

 pp. 181-183, 1914. 



