64 
LARAMIE BASIN, WYOMING. 
The selected crystals and cleanest material had 44 per cent of 
sodium sulphate, 55 per cent of water, a very small amount of other 
salts, and less than one-half of 1 per cent of insoluble material. No 
iron is reported. 
The deposits 1 2 miles north of old Rock Creek station are in an area 
of Chugwater red beds. There are many small depressions in the 
region, varying in size upward to 90 acres. They are usually dry or 
miry except in rainy seasons. The deposit ranges from a thin crust to 
a bed several feet thick and the composition varies. Ordinarily 
there is a regular gradation from a preponderance of sulphate of soda 
on the north to a preponderance of sulphate of magnesia on the south. 
There is a small admixture of sodium chloride and dirt. According 
to Slosson a the deposits have the following composition: 
Chemical composition of the Rock Creek soda deposits. 
[Hypothetical combinations.] 
Water 
Insoluble 
Sodium sulphate (Na 2 S0 4 ) 
Sodium chloride (NaCl) . . 
Magnesium sulphate 
44.50 ! 48.03 
.65 i .08 
12.13 24.49 
.38 .24 
42.34 27.16 
51.08 
1.13 
10.22 
.46 
37.11 
.58 
40. 52 
.42 
8.82 
27.71 
64.96 
1.20 
.66 
5. 47 
1. From surface of the largest of the lakes. 
2. From a depression in a small lake about a quarter of a mile north of the largest. 
3. From a large deposit about a mile north of the largest lake. 
4. From a deposit just north of No. 3. In this sample the sodium sulphate is between four and five 
times greater than the magnesium sulphate and it corresponds therefore rather with the ordinary 
Wyoming soda deposit than with the rest of the deposits of this group. 
5. Mud beneath No. 2. The salts contained in it are much the same as in the deposit above, but the 
proportion of chlorides is much greater. 
All these samples were collected by W. C. Knight in February. 1898. 
SULPHATE OF MAGNESIA. 
The mineral epsomite, or Epsom salts, occurs in several small lake 
basins 3 miles north of Wilcox station, on the Union Pacific Railroad. 
The largest lake, known as Brooklyn Lake, has an area of 90 acres and 
is covered with a deposit of nearly pure Epsom salts. The following 
analysis has been furnished by Wilbur C. Knight: 
Analysis of epsomite from Brooklyn Lake. 
Insoluble residue 0. 08 
Magnesium sulphate t> 51. 22 
Water 47. 83 
Chloride of sodium, calcium, and magnesium .42 
Iron Trace. 
Lost 45 
a Bull. Univ. Wyoming No. 49, 1901, p. 114. 
t> Containing a small percentage ol calcium and sodium sulphates. 
