GYPSUM, SALT, BORAX, AND SODA. 
The mineral products grouped under the above heading, though 
applied to widely different uses, form a somewhat natural group so 
far as origin is concerned. Their close connection becomes obvious 
when their study in the field is attempted, for it is commonly the case 
that two or more of these salts will be found in adjacent and closely 
related deposits. This is due to the mode of origin of such deposits. 
The materials here grouped include certain sulphates, chlorides, car- 
bonates, or borates of lime, magnesium, sodium, or potassium; and 
deposits of commercial value are due in almost every case to the 
deposition of these salts, by evaporation, from the sea or lake water 
in which they were contained in solution. 
The most important, and fortunately the most widely diffused, of 
these materials is common salt, whose uses, both in the preparation 
and preservation of food and in the chemical industries, are rapidly 
increasing. For a report on field work by the Survey, during 1902, on 
the Virginia salt and gypsum deposits see pages 406-416. Appended 
to this report are tables of analyses of rock salts, brines, and commer- 
cial salts from various United States and foreign localities. 
The next in importance of these materials is gypsum. In addition to 
the report on Virginia gypsum, noted above and presented in this bul- 
letin, all the commercially important gypsum deposits of the United 
States will be described .in a bulletin of the United States Geological 
Survey, now in preparation. 
A report on the California borax deposits has recently been issued 
by the Survey. This, together with other Survey publications on the 
materials of this group, will be found listed on page 417. The parts 
of that paper dealing with the worked deposits are here presented 
under the title of .Borax^deposits of Eastern California. 
BORAX DEPOSITS OF EASTERN CALIFORNIA. 
By M. R. Campbell. 
INTRODUCTION. 
The occurrence of deposits of borax in the United States, so far as 
known, is limited to the States of California, Nevada, and Oregon. 
The industry has passed through several stages of development since 
its inception in this country. Originally borax was obtained by evap- 
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