POTASH SALTS AND OTHER SALINES IE" THE GREAT BASIN REGION. 65 
CALCAREOUS DEPOSITS ABOUT THE SHORES. 
Tufa deposits have been found about the shore lines of many of the Quaternary 
lake basins. They are not so conspicuous in Bonneville as at Lahontan or Mono. 
They have been reported from Searles and Owens Lakes. The origin of this tufa, its 
composition and mineralogy, have been discussed by Russell and Gilbert, 1 and it is 
not important that they be repeated here. The significant feature of these deposits 
is their potassium content. Gilbert quotes analyses from the Fortieth Parallel Survey 
which show 0.22 per cent potassium. This is significant, as it indicates one way in 
which potassium compounds separate out from lake waters. The deposits are of no 
commercial interest. They have been an important means of interpreting the events 
of the Quaternary history. 
POTASH-RICH MINERALS. 
Of the soluble potash -rich minerals kalinite and niter are the only two known as min- 
eral species in the basin region. Undoubtedly potassium chloride and sulphate are 
associated with the bedded salines, but no distinct mineral species has been reported. 
The insoluble potash minerals, with the exceptions noted below, are associated 
with other rock-forming minerals in igneous rocks. Rocks containing notable quan- 
tities of potash-rich minerals are inconspicuous. Ransome 2 reports a leucite basanite 
from the Bullfrog district, Nevada, but this rock contains a very low percentage of 
potash. 
The occurrence of alunite has been discussed already. Jarosite contains from 6 to 
9 per cent potash. This mineral is not uncommon and has been reported from Tono- 
pah, Goldfield, and Bullfrog, Nev. It is associated with quartz and, in the occurrence 
at Goldfield. it is" found in an altered tuff. 3 It does not occur in quantity and is of no 
economic importance. Orthoclase has been reported, but, so far as known, no notable 
amounts of this mineral are available. Adularia has been reported from Jarbridge, 
Nev. The analyses show a potash content ranging from 11.84 to 15.12 per cent. 4 The 
mineral occurs associated with quartz in veins. With the exception of the alunite 
deposit noted in a previous section, the possibility of finding workable deposits of 
potash-rich minerals or rocks is not good. 
GYPSUM- 
Three types of gypsum deposits are found in the basin region — rock gypsum, gypsite, 
and lake gypsum. Rock gypsum occurs in Nevada at Mound House, Gerlach, Love- 
lock, Table Mountain, the Ludwig mine in Mason Valley, and at Arden, Clark County. 
At Mound House and Lovelock the gypsum is associated with limestone. At Mound 
House, Gerlach, and the Ludwig mine the surface gypsum passes into anhydrite at 
depth. Probably in all cases the rock gypsum is associated with rocks of Triassic age. 5 
At Mound House gypsite occurs in thin beds upon a number of low, crescent-shaped 
terraces which are a part of the alluvial slope between the rock gypsum deposit and 
the Carson River. It has undoubtedly been derived from the erosion and partial 
solution of the rock gypsum deposits above. Seepage and surface waters have caused 
the concentration of the gypsum in beds varying from 2 to 3 feet in thickness. The 
material is of a pulverulent nature. Analyses taken from several of these beds and at 
a number of different points are given in the following table: 
Analyses of samples from gypsum deposits. 
[Samples collected and analyses made by G. J. Young.] 
Constituent. 
Sample No.— 
1 
2 
3 
4 
5 
6 
7 
8 
Gypsum 
Per cent. 
59.79 
14.01 
26.13 
Per cent. 
68.20 
12.83 
8.72 
Per cent. 
79.51 
8.72 
11.78 
Per cent. 
53.94 
12.58 
33.48 
Per cent. 
50.43 
13.58 
35.98 
Per cent. 
82.75 
6.35 
10.80 
Per cent. 
79.81 
8.82 
11.33 
Per cent. 
72.37 
Calcium carbonate . . . 
5.21 
22.39 
1 Monograph 1, p. 167, Gilbert; 11th Annual Report, p. 187, Russell; 
94 I C Russell 
2 Bui'. No. 407 j U. S. Geol. Survey, p. 58. 
3 Professional Paper No. 66, U. S. Geol. Survey, p. 108. 
* Bui. No. 497, U. S. Geol. Survev, p. 52. 
5 See G. D. Louderback, Bui. No. 223, U. S. Geol. Survey, p. 118. 
20814 14- 
Bul. No. 108, U. S. Geol. Survey, p. 
