Montana Gypsum Deposits — Kowe. 105, 
deposits as any state in the Union, and in a few years this 
natural resource will be of great benefit to her citizens. 
The gypsum deposits in Montana may be divided into 
three general fields ; the North, Middle, and South Fields. 
These fields follow the contour of the mountains and run 
from northwest to southeast through the state. 
Little is known of the North Field, but it is claimed that 
some good deposits are located near Libby, Flathead county, 
Montana, and until recently a plaster of Paris and stucco 
mill was in operation at that place.* 
The Middle Field is located in the counties of Cascade 
and Fergus. Two large deposits are found in this field. 
One deposit near the towns of Armington and Kibby in Cas- 
cade county ; and the other in the Big Snowy mountains, of 
Fergus county, near Portuguese. The South Field is lo- 
cated in Carbon county, near Bridger. 
The selenite variety of gypsum is found in all the coun- 
ties of Montana east of the rockies. It occurs in the upper 
Cretaceous formations, but seldom is found in commercial 
quantities. "Very commonly it impregnates the waters 
both of streams and springs, making them unfit for use. 
At Hunter's Hot Springs, on the North bank of Yellowstone 
river, about 20 miles east of Livingston, the hot waters are 
now depositing gypsum and the old hot spring fissures are 
filled by a mass of gypsum and stilbite. Up to the present 
time fhese deposits, although of considerable extent, have 
not been utilized.''* 
During the summer of 1902 the writer found a vein of 
selenite in the southern part of Fergus county, near Folsom, 
which is about 18 inches thick and several yards in length. 
This deposit is in the Laramie. Many such places occur in 
the state but the areas are small and do not warrant an at- 
tempt at commercial production. 
Crystals of selenite gypsum are found in quite large 
quantities in tlie Laramie clays of Dawson county,'' and near 
Bear Paw mountains, in Choteau county. 
* Eighth Report of Bureau of Agriculture, Labor and Industry of the 
State of Montana. — FEutuisoN. 
*W. H. Weed, in Bulletin, T^. S. Geological Survey, No. 223. 
tJ P ^o-wv. - Nodular Barite and Selenite Cry'stah of Montana: American (Jeol- 
oGisT, vol, 33, p. 190. 
