298 Hillebrand and Washington — Minerals from Utah, 



Art. XXV. — Notes on certain rare Copper Minerals from 

 Utah ; by W. F. Hillebrand and H. S. Washington. 



[Read before the Colorado Scientific Society, Jan. 2d, 1888.] 



Some time since analyses and partial descriptions of several 

 rare copper minerals, from the American Eagle Mine, Tintic 

 District, Utah, were published * by one of us. These minerals 

 had been found by Mr. Richard Pearce in ore shipments from 

 that mine to the Boston & Colorado Smelting Works, near 

 Denver, Colorado. Later, in shipments from the neighboring 

 Mammoth mine, in the same district, Mr. Pearce discovered a 

 second series of minerals of similar character, most of the 

 species, however, being distinct from those of the former oc- 

 currence. In recent papers f he has given the results of his 

 examinations and enumerated the following species : enargite, 

 olivenite, conichalcite, clinoclasite, brochantite, pharmacosider- 

 ite, tyrolite(?), erinite, chalcophyllite, malachite, azurite, and 

 one or two others of doubtful identity, of most of which 

 " enargite is the mother mineral." 



In order that this interesting series, in part new to America, 

 might receive fuller study than he was able to devote to it, 

 Mr. Pearce with the assistance of Mr. Whitman Cross kindly 

 selected a set of specimens for examination in the laboratory 

 of the U. S. Geological Survey at Washington. The chemical 

 work of this paper was there carried out by one £ of us, while 

 the crystallographical and optical study was undertaken by the 

 other § at New Haven under the guidance of Prof. E. S. 

 Dana. The results of our work, both chemical and physical, 

 failed to meet all the hopes induced by a first view of the 

 material at disposal, although this was the best that could be 

 found. They are of sufficient interest, however, to make pub- 

 lic, especially in view of the meager state of our knowledge 

 regarding a majority of the species herein mentioned. 



1. Olivenite. 



This mineral occurs well crystallized ; its habit is prismatic 

 and tabular parallel to a (100, %-l) and the crystals are, as usual, 

 very simple as shown in the figure. The planes o (010, i-t) 

 and v (101, i-l) as a rule are either absent or very small. Meas- 

 urements were made for the purpose of obtaining a more exact 

 axial ratio than we have at present, the old values of Phillips 

 dating back to 1823. 



*Proc. Colorado Sci. Soc, i, 112, and Bull. TJ. S. Geol. Survey, No. 20, p. 83. 



f Proc. Colorado Sci. Soc, ii, 134, 150. 



% W. F. Hillebrand. § H. S. Washington. 



