303 PROCEEDINGS OP THE ACADEMY OP 



Again calculating 2 Cu ==Pb, we have the same formula as with the crystals. 



Cu 

 Pb 



As 



Sb 



S 

 I have seen but one specimen of this mineral, which was given me by Joseph 

 A. Clay, Esq., having been sent to him from Peru by his brother Hon. J. Randolph 

 Clay, United States Minister to that country. It was labelled "Pabonado en 

 Rocicler de Aranzazu." The appearance of the massive mineral is not unlike 

 some of the gray coppers, though its color is more of a bluish gray. This 

 peculiarity together with the bronze tarnish of its surface, with the blue spots 

 of Covelline (?) and the excess of lead as shown by blow-pipe examination, in- 

 duced me to make a quantitative analysis of both the massive mineral and the 

 crystals. The entire specimen was small, and the proportion of the crystallized 

 mineral being also small, I was obliged to make the examination with a very 

 limited amount of material. The determination of the specific gravity must be 

 deferred until more of the mineral is obtained. 



I name this mineral in honor of the Messrs. Clay, whose interest and exertions 

 in mineralogy are so well known to mineralogists in this country and abroad. 



The protracted illness of Prof. J. D. Dana, and his subsequent departure for 

 Europe, prevented his measurement of the microscopic crystals which I had 

 sent to New Haven. 



Stromeyerite. 



The specimen of this mineral which I obtained from the cabinet of Joseph A. 

 Clay, Esq., was remarkable as resembling, in many of its characters, the mine- 

 ral Sternbergite more than Stromeyerite. A blow-pipe examination, in which 

 I found copper, together with the want of flexibility in the crystals, and their 

 high lustre, led me to refer the mineral to Stromeyerite. To decide this doubt- 

 ful point, I picked out with difficulty a little of the pure mineral for analysis. 



The mineral is from Copiapo, Chili. It occurs in small six-sided aggregated 

 crystals belonging to the trimetric system, not exceeding an eighth () of an 

 inch in diameter, which are implanted on minute quartz crystals, forming 

 rose-like or fan-like clusters, having the striae of distinctly marked, and with 

 striae on the edges. In its appearance (as before mentioned) it is more like 

 Sternbergite, but differs by the absence of flexibility, and also possesses more 

 lustre than any specimens of Sternbergite which I have seen. 



Hardness from' 2-5 to 3. Lustre metallic: color dark steel gray: streak 

 nearly black and shining. Sectile, does not soil paper : crystals brittle. 



The Stromeyerite occurs in small veins and fissures in barytes, the sides of 

 which are lined with very small quartz crystals and associated with small crys- 

 tals of Pyrargyrite. 



Before the blow-pipe on charcoal fuses to a white globule, somewhat malle- 

 able, which, with the fluxes, gives the reaction of copper: with carbonate of 

 soda gives the reaction of sulphur. 



The following are the results of my analyses : 



I. II. III. 



Sulphur 16-35 per cent. 16-49 per cent. 



Silver 69-59 66-39 



Copper 11-12 " 



Iron 2-86 



99-92 

 The silver determination of (III.) was from 

 a little Pyrargyrite. 



Per cent. 



Sulphur 16-35 



Silver 69-59 



Copper 11-12 



Iron 2-86 



[N- 



ov 



