MONTANA 25 



from one to six inches of what appears to be a gray ashy 

 material. On close examination this proves to be crystals 

 of salt together with flocculent clay. Immediately under 

 this is found the shale in place. Samples of the clay and 

 gray ashy material, and the shale in place were taken 

 separately, and the analyses show the nitrate contents of 

 each. 



"The dark-colored shales show numerous crystals of 

 gypsum in the cracks and bedding planes. Where the 

 shale is dry and considerably weathered the gypsum 

 appears like white flour. In the seams of the shale, but 

 a foot or more under the surface in the same place, the 

 crystals are still firm and solid. 



"At Emery, Utah, the gypsum crystals were not only 

 taken out of the bedding plane of the thick layers, but 

 numerous cross fractures were found which were also 

 filled with gypsum crystals. Many of these cross fractures 

 were as much as a half inch thick and pieces of gypsum 

 this thickness and a foot long were removed from the 

 shales. 



" Montana. Overlying the Mancos is the Montana 

 Mesa Verde formations which are essentially sandstones, 

 shales, and grits, light gray to dark brown in color. Car- 

 bonaceous shales with thick beds of workable coal occur 

 near their base, while sandstone occurs in the upper part. 

 1 Transition marked by increase of sandstone upward and 

 appearance of brackish and fresh water arise instead of 

 marine conditions.' 



"The upper layers of sandstone are often found in thick 

 lenses and in many places contain high percentages of 

 gypsum. The vegetation accumulated in these shallow 

 seas resulted in the formation of coal. The sea seems to 

 have increased sufficiently after the formation of the coal 



