462 BULLETIN" 131, UNITED STATES NATIONAL MUSEUM 



sulphides. This white powdery material upon solution in water and 

 recrystallization gives green nielanterite crystals. It occurs as a 

 pasty greenish-white material in cavities in decomposing pyrite from 

 the Evolution prospect near Osburn. Certain fine grained massive 

 pyrite from the Last Chance mine when placed in dry air becomes 

 coated with a fine frost-like growth of delicate fibers of melanterite. 



CHALCANTHITE (755) 



BLUE STONE, BLUE VITRIOL 



Hydrous copper sulphate, CuO.S0 3 .5H 2 0. Trielinic. 



Chalcanthite or native blue vitriol commonly forms where copper 

 sulphides are exposed to weathering, but being very soluble in 

 water it seldom accumulates in any quantity except in very dry 

 situations. In desert States this mineral sometimes occurs in large 

 enough bodies to be of importance as an ore but in most Idaho 

 districts the rainfall is so heavy that water-soluble minerals are rare. 

 The following occurrences have been noted : 



ADAMS COUNTY 



Chalcanthite is reported by Livingston and Laney to occur in 

 oxidized copper ores of the contact copper deposits of the Seven 

 Devils district and also to be present in solution in the waters from 

 the tunnels of the Red Ledge mine as shown by the fact that a bright 

 piece of iron immersed in the mine waters becomes quickly coated 

 with copper. 67 Bell 68 states that copper sulphate occurs interlayered 

 with iron sulphate and native sulphur in masses several centimeters 

 thick in little caves at the foot of the cliff at the Red Ledge mine. 



BOISE COUNTY 



Chalcanthite occurs as a pale blue efflorescent crust on a specimen 

 of pyritic ore from the dump of the lower tunnel of the Mohawk 

 mine, Summit Flat district. 



CUSTER COUNTY 



Chalcanthite occurs in the Alder Creek (Mackay) district in the 

 ores of the Copper Bullion mine as thin coatings composed of dis- 

 tinctly fibrous crystals. 69 



A specimen of partly oxidized chalcopyrite-limonite ore from the 

 surface workings of the Lost Packer mine is partly incrusted with a 

 pale blue efflorescence. The blue mineral which is a water soluble 

 copper sulphate is very pale blue under the microscope and is biaxial 

 negative with 2V large, dispersion r<v pronounced, /3 index of refrac- 



«" Idaho Bur. Mines and Geol. Bull. 1, pp. 55 and 07, 1920. 



w Robert N. Bell. Ann. Rep., State Mine Inspector for 1913, p. 1G7. 



«« J. B. Umpleby. U. S. Geol. Survey, Prof. Paper 97, p. 50, 1917. 



