182 



umpleby: crystallized chrysocolla 



the pure material grades into ferruginous chrysocolla and copper 

 pitch ore, and traversing it are ill-defined layers of malachite; 

 films of kaolin occur along minute fractures. The physical prop- 

 erties of this massive form are: hardness, about 3; density, 2.4 

 (Jolly balance determination not satisfactory, because of many 

 minute fractures) ; luster, somewhat waxy ; color, beryl green 

 (Ridgway's color scale); streak, white; tenacity, brittle. 



Examined microscopically both in refractive index solutions 

 and in thin section the mineral is seen to have one distinct cleav- 

 age normal to the elongation and possibly one parallel to it, al- 

 though what appears to be cleavage in the latter direction may 

 be merely an overlapping of fibers. It is uniaxial, optically 

 positive, has positive elongation, and is highly birefringent. 

 The indices of refraction are W, 1.46 and E, 1.57 ±, a small varia- 

 tion in the values from different grains making it impossible to 

 place a satisfactory value in the third decimal place. Thick 

 grains show pleochrbism in colorless (W) and pale bluish green 

 (E) tones. The mineral belongs to the hexagonal or to the tet- 

 ragonal system of crystallization. 



Partial Analysis of Chrysocolla, E,. C. Wells, Analyst. 



A partial analysis of the massive material, carefully selected 

 with a hand lens, was made in the chemical laboratory of the 

 United States Geological Survey in order to make certain that 

 the material was chrysocolla. Although the analysis is unsatis- 

 factory in that it only totals 97.7 per cent, it is beheved that the 

 results prove that the crystalline substance is chrysocolla. 



