POTASH SALTS AND OTHER SALINES IN THE GEEAT BASIN REGION. 51 
that crystallization must proceed at a comparatively slow rate under natural condi- 
tions at the beginning of desiccation, and, as desiccation proceeds, the rate of crystal- 
lization must increase to a maximum. Final desiccation of the mother liquors must 
be a long drawn-out process, if at all completed. It is not impossible to expect that 
at this stage of desiccation sedimentation by eeolian action might proceed rapidly 
enough to absorb the final mother liquor. The crystalline mass formed during the 
final stages of desiccation would also absorb portions of the mother liquor at the end. 
The saline content of a mud, assuming that it has absorbed a brine which is saturated 
and at point of crystallization, has been calculated in the 'following: A wet mud 
with a specific gravity of 2 and composed of mineral particles 2.6 would have a void 
space of 37.4 per cent by volume. If 1 cubic foot were filled with a brine of specific 
gravity 1.25, the brine would weigh 29.3 pounds. Chatard's experiments on the 
Owens Lake water showed a brine of 1.26 specific gravity at incipient crystallization; 
and this contained 30.56 per cent by weight of salines. The brine filling 1 cubic foot 
of the mud would contain approximately 9 pounds of salines. This would be equiva- 
lent to 8.1 per cent of the weight of the dry mud. 1 Dry mud samples containing an 
excess of 8.1 per cent of saline material would indicate saturated solution conditions 
with some crystallization and deposits of salines; less than 8 per cent it would be con- 
cluded that the mud had captured an unsaturated brine. 
If it is assumed that the mass of saline crystals would contain a void space of 30 
per cent of its volume and the resulting mother liquor had a specific gravity of 1.3, 
the weight of the brine solution contained in 1 cubic foot would be 24.4 pounds. If 
we assume the specific gravity of the salines to be 1.9, the weight of the brine absorbed 
would be 29.0 per cent of the weight of the dry saline material, or 22.4 per cent of 
weight of brine and salt. This would not be sufficient to absorb all of the mother 
liquors at the final stages of crystallization. 
Interpreting the chemical data obtained by the deep bore and the three surface 
bores, and using the criteria which have been established, I have reached the con- 
clusion below. 
The initial stages of Searles Lake. were similar to Lake Lahontan. The lake at thia 
period might have been over 1,200 feet in depth, and there is no reason to suppose 
that it was other than fresh. The drying up of the lake must have extended over a 
great length of time. The first part of the record, 600 to 627 feet, indicates that the 
lake had reached saturation and had begun to deposit salines. The brines at this 
stage deposited salines low in carbonates, high in chlorides and sulphates, and notice- 
ably high in potassium. Either sedimentation proceeded at a rapid rate or crystal- 
lization must' have been slow. The latter is more likely the case. At a depth of 
586 to 596 feet the brine was diluted sufficiently to stop crystallization. The saline 
content of this brine figures out as follows: 
Per cent. 
Potassium chloride 5. 48 
Sodium chloride 59. 15 
Sodium sulphate 29. 04 
Sodium carbonate 1. 31 
Sodium bicarbonate 2. 44 
During this stage carbonates were accumulating in the lake waters. Concentra- 
tion of the water followed and salines were again deposited (575 to 580 feet; samples 
Nos. 223 and 224). From 427 to 540 feet salines were steadily deposited and inclosed 
by the sediments. The brine at this stage must have approximated in composition 
evaporated Owens Lake water, for carbonates are found in increasing amounts. The 
conditions must have approximated the trona period. During this period the rate 
of crystallization exceeded sedimentation. The content of potassium is high. From 
227 to 427 feet the record is lacking. At 227 feet conditions approaching the sul- 
phate period are indicated. The salines are low in carbonates and high in sulphates 
and chlorides. Potassium still remains high and amounts to 3.72 per cent of the 
saline residue (sample 211). . From 80 to 227 feet the record is lacking. 
The central bore of the Dolbear series indicates that at 65 to 79 feet depth the 
trona period occurred, followed at 50 to 65 feet by the sodium chloride period, 
and this was followed by a sulphate period at .35 to 50 feet. An interruption is indi- 
cated here. More than likely a humid period diluted the lake and stopped crystalli- 
1 From experiments upon slime cakes formed by vacuum filtration, I have found that the densest por- 
tion of a slime cake, formed under a pressure of 11 pounds per square inch, has a specific gravity of 1.84, 
and a water content of 27.9 per cent. Using these figures and assuming a brine of 1.3 specific gravity and a 
saline content of 30 per cent by weight would give a saline content for the dried cake of 13 per cent. This 
figure can be used comparatively with the one obtained by calculation. I am inclined to use the figure 
obtained by the previous calculation, since the slime experiment does not take into account the time element 
nor the greater pressures to which mud in the bottom of a lake would be subjected. 
