306 Hillebrand and Washington — Minerals from Utah. 



emerald to bluish green. Schrauf s number for the sp. grav 

 (2 - 66) is unquestionably much too low. That of the material 

 now analyzed was 3 - 79 at 23J° C. When treated with dilute 

 nitric acid it becomes at once covered with the brilliant white 

 coating of bismuth arseniate so characteristic of mixite. The 

 latter mineral is stated to belong to the monoclinic or the tri- 

 clinic system, while the observations of Mr. Whitman Cross 

 would indicate that the present one can belong to neither of 

 those systems. He says :* " The needles are very slender, with 

 a length of more than l mm in some cases, by 0'5 mm . They are 

 deeply striated vertically, and the crystal system could not be 

 determined, although the extinction in polarized light makes 

 reference to the tetragonal, the hexagonal, or the rhombic sys- 

 tem necessary. The index of refraction is high. Pleochroism. 

 distinct, the colors observed being for the thicker crystals, a 

 (and h) sea green, c sky blue." 



1. Pharmacosiderite. 

 No analyses were made for want of sufficient material. 



8. Brochajsttite. 



This hydrous sulphate of copper occurs in two distinct types 

 in the specimens examined. The first, or ordinary brochantite, 

 is of a prismatic habit as is shown in fig 6. The crystals are 

 dark green and transparent, but do not give good measure- 

 ments, owing to the imperfection of the surface. The cleavage 

 parallel to h (010, i-%) is perfect. The measured angle of 

 m^h, 110/\010 = 51° 46', is only approximate, and differs con- 



siderably from Miller, who gives 52° 5 r , and Schrauf, who 

 gives 52 . 



* Proc. Colorado Sci. Soc, ii, 153. 



