228 DESCRIPTIONS OF MINERALS. 



north of trail from Mono Lake, is a deposit. 10 miles long 

 by 7 wide, of borates and other salts, chiefly borax, calcium 

 borate, sodium sulphate, and common salt. The large de- 

 posits of *• priceite" in Southern Oregon, and of nlexite, in 

 the " Cane Spring District/'' 20 miles west of San Bernar- 

 dino, and at the Columbus Marsh, are other sources of 

 borax. The amount of borax received at San Francisco 

 during the year 1ST6 was 5,180,910 pounds, and in 1877, 

 4,154,209 pounds. 



Nitre. — Potassium Nitrate. 



Trimetric. In modified right rhombic prisms. 1:1= 

 118° 50 '. Usually in thin white subtransparent crusts, and 

 in needleform crystals on old Avails and in caverns. Taste 

 saline and cooling. H = 2. G-=l*97. 



Composition. IL 3 X=Xitrogen pentoxide (X 2 5 ) 53*4, 

 potash ±6'6. Burns vividly on a live coal. 



Diff. Distinguished readily by its taste and its vivid ac- 

 tion on a live coal ; and from sodium nitrate, which it most 

 resembles, by its not becoming liquid on exposure to the 

 air. 



Nitre, called also saltpetre, is employed in making gun- 

 powder, forming 75 to 78 per cent, in shooting powder, and 

 62 in mining powder. The other materials are sulphur (10 

 per cent., for shooting powder to 20 for mining) and char- 

 coal (12 to 14 for shooting powder and 18 for mining). It 

 is also extensively used in the manufacture of nitric and 

 sulphuric acids : also for pyrotechnic purposes, fulminating 

 powders, and sparingly in medicine. 



01)8. Occurs in many of the caverns of Kentucky and 

 other Western States, scattered through the earth that 

 forms the floor of the cave. In procuring it, the earth is 

 lixiviated, and the lye. when evaporated, yields the nitre. 

 India is its most abundant locality, where it is obtained 

 largely for exportation. 



Spain and Egypt also afford large quantities of nitre for 

 commerce. This' salt forms on the ground in the hot weather 

 succeeding copious rains, and appears in silky tufts or efflo- 

 rescences : these are brushed up by a kind of broom, lixi- 

 viated, and after settling, evaporated and crystallized. In 

 France, Germany. Sweden, Hungary, and other countries, 

 there are artificial arrangements' called nitriaries or nitre 

 beds, from which nitre Is obtained by the decomposition 



