Hillebrand and Washington — Minerals from Utah. 299 



Fte. i. 



Upon examination and measurement with a Fuess horizon- 

 tal goniometer it was found that e^e' (01 1a Oil) was the 

 only angle sufficiently accurate for the 

 purpose, a and m being a little rough 

 and uneven. The angle mentioned fur- 

 nished a good value for c, but to obtain 

 the value for a, use had to be made of 

 a specimen of olivenite from the Ameri- 

 can Eagle Mine (No. 5684 in the Yale 

 University collection). This olivenite 

 was acicular in habit, the prism m 

 (110,*) predominating. From these crys- 

 tals good measurements were obtained 

 of m/\m'" (110 a HO) and a satisfactory 

 axial ratio deduced. The measured an- 



gles are as follows 



on 

 no. 



.011 = 67°51' 

 110 = 86°26' 



From these angles we obtain the following axial ratio, 



a:b:c = 0-93961 : 1 : 0-672606 



The measurements above differ considerably from the funda- 

 mental angles of Phillips, which are, 



e * e', 011 * 011 = 69°10' and m * m'", 1 10 * 110 = 87°30' 



giving the axial ratio, 



&:i-.c = 0-9573: 1: 0-6894 



Measurements were made with the view of determining 

 whether the species is really orthorhombic or not. The fol- 

 lowing are the angles obtained — 



a*e, 100*011 = 8 

 a*e', 100*011 = 



4-', a' , 



3 9', a' . 



100*011 = 89°59' 

 ', 100*011 = 90°1' 



It is seen that the front angles are in each case a trifle less than 

 the rear angles, but not much reliance can be placed on these 

 results, owing to the poor surface of both a (100) and a' (100). 

 Under the microscope the tabular crystals showed parallel 



extinction and a slight pleochroism, the vibrations || c being 

 pale olive green, while those || h were of a brownish yellow, 

 with the absorption h> c. 



The mineral was not analyzed because of the small quantity 

 available and because its identity was otherwise clearly estab- 

 lished. 



2. Ekinite. 



Erinite occurs as a dark green crystalline lining of cavities, 

 associated with and generally upon enargite, azurite, barite, or 



