400 BEPOKT OF NATIONAL MUSEUM, 1899. 



a tract of some 300 acres for a longer period than it does elsewhere; 

 but even here it nowhere reaches a depth of more than a foot. 



Between this 300-acre tract and the main flat lying a little lower 

 there interposes a slight ridge, which prevents the surface water from 

 escaping to the lower ground. 



The water of the lake is of a dark-brown color, strongly impreg- 

 nated with alkali, and has a density of 28 Baume. The salts obtained 

 from it by crystallization contain carbonate and chloride and borate of 

 sodium, with a large percentage of organic matter. 



Summarized, the following minerals have been found associated with 

 the borax occurring in the Searles marsh: Anhydrite, calcite, celes- 

 tite, cerargyrite, colemanite, dolomite, embolite, gay-lussite, glauber- 

 ite, gypsum, halite, hanksite, natron, soda, niter, sulphur, thenardite, 

 tincal, and trona, the most of these occurring, of course, in only minute 

 quantities. There is, however, reason to believe that hanksite will 

 yet be found abundantly, both here and in the other salines of this 

 region. 



The submerged tract above described is called the "Crystal Bed," 

 the mud below the water being full of large crystals, which occur in 

 nests at irregular intervals to a depth of 3 or 4 feet. Many of these 

 crystals, which consist of carbonate of soda and common salt with a 

 considerable percentage of borate, are of large size, some of them 

 measuring 7 inches in length. The water 15 feet below this stratum 

 of mud contains, according to Mr. C. N. Hake, who made, not long 

 since, a careful examination of these deposits, carbonate of soda, borax, 

 and salts of ammonia. The ground in the immediate vicinity, a dry 

 hard crust about 1 foot thick, contains, on the same authority: 



Sand 50 



Sulphate of soda 16 



Common salt 12 



Carbonate of soda 10 



Borax 12 



The borax here occurs in the form of the borate of soda only, no 

 ulexite (borate of lime) having yet been found. 



The chief foreign sources of borax salts are northern Chili, Stass- 

 furt in Germany,- Italy, Asia Minor, and Thibet. 



The Chilean mineral is ulexite and is reported as occurring through- 

 out the province of Atacama and the newly acquired portions of Chile. 

 Ascotan, which is now on the borders of the Republic, but formerly 

 belonged to Bolivia, and Maricunga, which is to the north of Copeapo, 

 are the places which have proved most successful commercially. The 

 crude material occurs in both places in lagoons or troughs, which, 

 instead of being entirely filled with common salt, as is usually the case 

 in the desert, contains zones or lavers of boronatrocalcite embedded 



