Larsen and Glenn — Melanterite, etc. 225 



Akt. XVI. — Some Minerals of the Melanterite and Chal- 

 canthite Groups with optical data on the hydrous sul- 

 phates of manganese and cobalt; 1 by Espee S. Laesen 

 and M. L. Glenn. 



Zinc-copper Melanterite and other members of the Melanterite 



Group. 



Introduction. — During the summer of 1916 one of the 

 authors (E. S. L.) found a secondary mineral in consider- 

 able amount in the dumps of the Good Hope and Vulcan 

 mines at Vulcan, Gunnison county, Colorado. The mines 

 are on a great body of sulphides made up chiefly of pyrite 

 with some chalcopyrite and sphalerite. The proportion 

 of the constituents, especially the sphalerite, varies 

 greatly in different bands of the ore. Thin seams of 

 quartz carrying gold and tellurium are present on the 

 walls of the sulphide body. The dumps carry thousands 

 of tons of this sulphide, in part massive, in part friable 

 and sandy in texture. Many of the interstices between the 

 fragments on the dumps are filled with a green, columnar 

 mineral which on study in the laboratory proved to be a 

 new member of the melanterite group, which carries about 

 equal amounts of copper and zinc and a little iron; the 

 name zinc-copper melanterite is proposed for the mineral. 



In adopting a name for this mineral as well as in adopt- 

 ing the names for the chalcanthite-like dehydration prod- 

 ucts of the members of the melanterite group, the authors 

 at first planned to follow the suggestion of Washington 2 

 and to designate the various members of the groups by 

 prefixes to the group names, melanterate and chalcanthate. 

 However, as there were so many objections from all the 

 mineralogists who were consulted and as it seemed proba- 

 ble the names would not be accepted and confusion would 

 result, the plan was adopted of using the usual group 

 name with the principal metals present prefixed to it. 

 Accordingly, the melanterites are minerals with the gen- 

 eral composition RO.S0 3 . 7H 2 ; they are monoclinic and 

 their properties are related to those of the common min- 

 eral melanterite. Zinc-copper melanterite is a melan- 

 terite in which R is chiefly Zn and Cu with Zn predomi- 



1 Published with permission of the Director of the U. S. Geol. Survey. 



2 Washington, Henry, S.; A suggestion for mineral nomenclature, this 

 Journal, vol. 33, pp. 137-151, 1912. 



