Hillebrand — Emmonsite (?) from a New Locality. 433 



Art. XLIY. — Emmonsite (?) from a New Locality ; by 



~W, F. HlLLEBRAND. 



Dr. Waldemar Lindgren, of the Geological Survey, col- 

 lected in the W. P. H. mine at Cripple Creek, Colorado, a green 

 mineral which has been observed in other mines there, and 

 which on examination in the laboratory showed close resem- 

 blances to the emmonsite described by the writer nearly twenty 

 years ago.* It differed from it, however, in outward appearance 

 by assuming mammillary forms instead of crystalline plates. In 

 its optical properties, so far as they were determinable, there is 

 perhaps no positive disagreement with those reported for 

 emmonsite. Mr. W.T. Schaller reports as follows : 



"There are two cleavages, one parallel to b (010) and another 

 parallel to a form in the orthozone. Axial plane parallel to h 

 (010). Ba? a perpendicular to a cleavage face in the orthozone. 

 The extinction on the clinopinacoid is inclined 25° to 30° to 

 the vertical axis. 2E is approximately 40°. Double refraction 

 medium, and the mineral non-pleochroic." 



The gangue in which the specimens were found is granite 

 and schist, close to their contact with a porphyritic breccia, in 

 a vein pocket, at a distance of about 150 feet from the surface. 

 Associated with it was very rich native gold ore and also tel- 

 lurite, though neither of these was apparent on the few speci- 

 mens that came to the laboratory. 



Like emmonsite, the mineral melts at a low heat to a red- 

 brown liquid, but, unlike it, gives on stronger heating only 

 tellurous oxide with no trace of selenium or selenious oxide. 

 Analysis confirmed the absence of selenium. Its density, too, 

 differs from that of emmonsite, if the determinations, in both 

 cases on scanty material, are to be depended on. After allow- 

 ing for gangue the original emmonsite was judged to have a 

 density of at least 5, while that of the present mineral is but 

 little above 4*53, after allowing for 22'44 per cent of gangue, 

 consisting mainly of quartz, and to which the specific gravity 

 of quartz was assigned. 



In its appearance the present mineral would seem to resemble 

 durdenite more than emmonsite, but the marked difference in 

 water content differentiates it sharply from that mineral, which 

 yields over ten per cent. 



After deducting 22*44 per cent of gangue containing over 

 90 per cent of silica, three portions of from 0*15 to 0*20 gram 

 net weight each gave the following results : 



*Proc. Colorado Sci. Soc, ii, 20, 1885. 



