116 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



anglesite and was rather highly argentiferous. In the Hypotheek 

 mine at Kingston covellite occurs in oxidized ore associated with 

 cerusite, bindheimite, etc., as pulverulent dark blue fillings of cavi- 

 ties. In the Liberal King and probably other veins a part of the 

 sphalerite is blue from covellite developed along seams. 



WASHINGTON AND ADAMS COUNTIES 



In the Seven Devils district covellite is found sparingly as a product 

 of downward secondary enrichment replacing chalcopyrite and bornite 

 along fractures in the contact copper deposits. It occurs in small 

 amount with chalcocite along fractures in chalcopyrite in fissure 

 quartz-feldspar veins in granite at the Lucky Strike mine, replacing 

 chalcopyrite at the Gaarden mine, or chalcopyrite and bornite at the 

 River Queen mine. 



GREENOCKITE (68) 

 Cadmium sulphide, CdS. Hexagonal, hemimcrphic. 



BLAINE COUNTY 



Greenockite lias been doubtfully identified as a yellow coating on 

 oxidized ore in the Plughof, formerly the Lark mine, 2 miles south- 

 west of Bellevue. 87a 



WURTZITE (69) 

 Zinc sulphide, ZnS. Hexagonal, hemimorphic. 



BLAINE COUNTY 



Wurtzite, the rare hexagonal form of zinc sulphide, occurs with 

 sphalerite in a group of late Tertiary veins in the Lava Creek and 

 Era districts in Blaine County, especially in the St. Louis mine in 

 the latter district. The gangue of these veins consists of cryp to- 

 crystalline quartz and chalcedony with, in places, some calcite and 

 barite. The ore minerals comprise galena, sphalerite, wurtzite, 

 pyrite, chalcopyrite, proustite, tetrahedrite, and argentite. These 

 occur in veins and, to some extent, replacing the wall rocks. Cerar- 

 gyrite, smithsonite, and cerusite are secondary minerals. In the 

 wall rocks sphalerite, pyrite, and wurtzite replace the minerals of 

 the inclosing lavas and tuffs. The sphalerite and wurtzite are, for 

 the most part, fine grained and without crystal outline, but locally 

 the wurtzite occurs in peculiar spherical masses 6 to 15 millimeters 

 in diameter. In cross section these arc made up of an outer band 

 of dark brown dense wurtzite separated from a large central light 

 brown area by a dense black layer, also of wurtzite. The inner light 

 brown core is spongy in texture and has a distinctly radial structure, 

 the interstices being filled by calcite.' Spherical bodies of wurtzite 

 occur in unaltered galena ore and are traversed by veinlets of galena. 87fr 



87 ° D. F. Hewett. Personal communication, 1923. 



a?* T. B. Umpleby. U. S. G30I. Survey, Prof. Paper 97, p. 86, 1917. 



