THE MINERALS OF IDAHO 461 



is exposed in short tunnels and pits in sections 7, 8, 17, and 18, 

 T. 13 N., R. 7 W., and occurs in lenticular masses banded with 

 grayish and greenish material, which range from 6 to 20 feet in 

 thickness. Some of the gypsum is pure white, massive, and spotted 

 with small lumps of impure gypsum and dark country rock; some is 

 yellowish, owing to lumps of foreign material; and some is filled with 

 laminae of a greenish mineral and small rolls of impure limy material. 64 



EPSOMITE (748) 



EPSOM SALT 



Magnesium sulphate, MgO.S0 3 .7H 2 0. Orthorhombic . 



Epsomite, the native mineral having the same composition as the 

 compound used in medicine under the name epsom salt, occurs some- 

 what abundantly with other saline minerals in the Homedale region 

 in Oregon and in adjacent parts of Owyhee County. 



OWYHEE COUNTY 



On Jump Creek epsomite occurs in the Claytonia saline claim west 

 of the Mc Cloud ranch mixed with sodium sulphate as a bed of coarsely 

 crystalline salts 10 inches thick. 65 



MELANTERITE (751) 

 COPPERAS 



Hydrous ferrous sulphate, FeO.SO a .7H 2 0. Monoclinic. 



Melanterite, having the same composition as the material called 

 copperas or green vitriol, is a common product of the oxidation of 

 iron sulphides but, owing to its easy solubility in water, it seldom 

 accumulates except under unusually dry conditions. It is present in 

 solution in many mine waters. The following occurrences have been 

 noted: 



ADAMS COUNTY 



At the Red Ledge mine, in the Seven Devils district, water per- 

 colating through the rock containing disseminated sulphides is heavily 

 charged with iron sulphate in solution and sulphates of iron, probably 

 melanterite, accumulate in thick crusts in sheltered places along the 

 Gaarden trail and elsewhere. No specimens of these sulphates have 

 been available for examination. 66 



SHOSHONE COUNTY 



Ferrous sulphate has been noted in a number of places in the Coeur 

 d'Alene district, usually as a white efflorescence on decomposing 



« R. W. Stone and others. Gypsum deposits of the United States, U. S. Oeol. Survey, Bull. 697, pp. 

 89-100, 1920. 

 « O. R. Mansfield. U. S. Oeol. Survey, Bull. 620, p. 30, 1916. 

 «» D. C. Livingston and F. B. Laney. Idaho Bur. Mines and Qeol. Bull. 1, p. 54, 1920. 



