THE BARITE DEPOSITS OF MISSOURI 35 



sandy, and all of it is more or less cherty. The sandstone shows 

 conglomeratic phases here and there, and there are two or three 

 layers of chert breccia. 



The dolomite consists essentially of dolomite and calcite, 

 with chert and glauconite and rarely pyrite as accessory consti- 

 tuents. The calcite is often in masses a couple of inches in di- 

 ameter. The color ranges from bluish-gray to buff or yellow- 

 ish-gray. A few beds are pinkish and here and there some are 

 almost white. The dolomite varies in texture from coarsely cry- 

 stalline to very fine-grained, with some beds that are porous. The 

 microscope shows the typical anhedral grains of a dolomite, the 

 grains having irregular boundaries. The chemical composition 

 of the Gasconade dolomite (composite analysis) is as follows: 



SiO^ 2.94% 



Fe^O, ] 



V 52 



FeO ) 



AI2O3 16 



CaO 31.40 



MgO 18.10 



CO2 45.70 



H,0 ....... .43 



99.25% 



The sandstone consists of angular grains of quartz with 

 some chert fragments. Most of the quartz grains show crystal 

 faces, only a few being rounded. Qn the other hand the chert 

 particles are well rounded and white. They weather out leaving 

 small round or oval cavities in the sandstone. In places the chert 

 fragments are large enough to make the rock conglomeratic. 

 There are also some equally large quartzite pebbles in a sandstone 

 bed near the top of the formation. The sandstone is cemented 

 with silica in many places and thus becomes a quartzite. In other 

 places the cement is hematite and limonite, while rarely it is dolo- 

 mite or calcite. The sandstone is usually some shade of red, 

 white, gray or yellow. It is medium to fine-grained, save in the 

 conglomeratic phase. 



