POTASH SALTS AND OTHER SALINES IN 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,' 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 a.n 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^ reports a leucitebasanite 

 from the Bullfrog district, Nevada, but this rock contains a very low percentage of 

 potash. 



The occurrence of aiunite 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.' 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.^ The 

 mineral occurs associated with quartz in veins. With the exception of the aiunite 

 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.^ 



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 dififerent 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. . . 



Insojiihlfi 



5.21 

 22.39 







1 Monograph 1, p. 167, Gilbert; lltb Amiual Report, p. 187, Russell; Bui. No. 108, U. S. Geol. Survey, p. 

 94, 1. C. RusseU. 



2 Bul. No. 407, U. S. Geol. Survey, p. 58. 



3 Professional Paper No. 6fi, U. S. Geol. Survey, p. 108. 

 i Bul. No. 497, U. S. Geol. Survey, p. 52. 



5 See G. D. Louderback, Bul. No. 223, U. S. Geol. Survey, p. 118. 



20814 14 5 



