THE MINERALS OF IDAHO 



425 



ite is associated with a bright yellow-green alteration product of 

 earthy texture which consists in the main of scorodite but which 

 contains some olivenite. 



Under the microscope the olivenite is transparent and pale blue- 

 green in color. Optically it is biaxial positive with 2E large, disper- 

 sion perceptible r<v. Sections perpendicular to an optic axis show 

 no extinction in white light. The a index of refraction is below 1.79 

 while j8 and 7 are above 1.79. It is easily soluble in cold dilute hydro- 

 chloric acid and gives qualitative reactions for copper and arsenic. 

 It contains no iron. 



The crystals are somewhat dull externally and are not well suited 

 for goniometric measurement. They have the habit shown in 

 figure 137. The angles measured are as follows: 



Measurements of olivenite from Lemhi County 



The form Z(043) is new for olivenite but, in view of the close 

 agreement between the measured and calculated angles it can be 

 regarded as well established. 



TRICHALCITE (596) 



Hydrous copper arsenate, 3CuO.As 2 05.5H 2 0. Orthorhombic. 



The rare arsenate, trichalcite, has been identified optically in a 

 specimen from the Liberal King vein in Shoshone County as described 

 in a previous paper. 29 



SHOSHONE COUNTY 



The specimen containing the trichalcite -is from the dump of the 

 upper tunnel of the Liberal King claim which adjoins the property 

 of the Lookout Mountain Mining Co. on the high mountain east of 

 the forks of Pine Creek. 



On the dump of this tunnel there is a heap of porous quartz, con- 

 taining original pyrite, arscnopyrite, and chalcopyrite, which is 

 brilliantly colored by secondary blue, green, and yellow oxidation 

 products in thin films. The most abundant of these minerals, the 

 blue-green one, has a vitreous to pearly luster and resembles tyrolite. 



28 Earl V. Shannon. Mineralogic notes on pyrite, pucherite, trichalcite, and wavellite. Proc. U. S , 

 Nat. Mus., vol. 62, art. 9, 1922. 



