172 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



HALITE (166) 



ROCK SALT 



Sodium chloride, NaCl. Isometric. 



BANNOCK COUNTY 



Salt has been obtained for many years from saturated salt brines 

 which are obtained from brine springs which seep from barren 

 patches of stony gravel in the valley bottoms on Kock Creek, Crow 

 Creek, and Tygee Valley. White salt often forms a crust about 

 these springs which are probably underlain by extensive deposits of 

 rock salt. In deepening a spring in Crow Creek Valley, 38 miles 

 northeast of Montpelier, rock salt was encountered 6 feet below the 

 surface. This was penetrated to a depth of 20 feet without reaching 

 the bottom of the deposit. This salt is exceptionally pure sodium 

 chloride. 61 



OWYHEE COUNTY 



Sodium chloride occurs in small amount mixed with epsomite, 

 gypsum, nitrates, etc., in nitrate prospects on Jump Creek, Sucker 

 Creek, and in adjoining regions southeast of Homedale, Oreg. 62 



CERARGYRITE (169) 



HORN SILVER 



Silver chloride, AgCl. Isometric. 



Cerargyrite is, in Idaho as in most other silver producing States, 

 the most important and in many mines the only important silver 

 mineral in the oxidized ores. Unless present in considerable amount 

 it is very inconspicuous and is liable to be unnoticed in rusty quart- 

 zose ores in which it is present in some abundance. Ores which are 

 leached and cellular from oxidation yet which contain high values 

 in silver are commonly called chloride ores, even though the cer- 

 argyrite may never be present in visible grains. There is a tendency 

 which has been noted among Idaho miners to refer to as "chlorides" 

 any yellowish or greenish yellow coloration in the oxidized ores. 

 This is incorrect as. the silver chloride is rarely yellow. These so 

 called "chlorides" are usually ocherous bindheimite, an antimonate 

 of lead although pyromorphite is also called chloride ore. 



Where present cerargyrite is usually in grains, globules, or thin 

 crusts on quartz mixed with limonite. It may be recognized by its 

 softness and sectility and by its property of turning grayish lavender 

 in color when exposed to sunlight. 



61 C. L. Breger. U. S. Geol. Survey, Bull. 430, p. 555, 1910. 



« G. R. Mansfield. U. S. Qeol. Survey, Bull. 620, pp. 19^4, 1910. 



