THE BARITE DEPOSITS OF MISSOURI 55 



of rock in varying amounts. The lenticular character of the 

 sandstones is evidence of the shifting of the areas of deposition, 

 v^hile the sun-cracks, cross-bedding, and ripple-marks give ample 

 proof of shallow water. The abundance of chert is significant 

 in view of the absence of shale. This is, however, a characteris- 

 tic of the Cambrian and Ordovician formation of the Ozark re- 

 gion. 



ECONOMIC GEOLOGY 



MINERALOGY OF THE BARITE DEPOSITS 



The mineralogy of the deposits is comparatively simple. 

 Only a few minerals are found with the barite. Sulfides, oxides, 

 carbonates, silicates, and sulfates are the groups represented. 

 The usual mineral association is quartz, pyrite or marcasite, 

 limonite (pseudomorphic after pyrite or marcasite), galena, 

 sphalerite, and barite. While any one or all, save barite, may be 

 missing at a given locality, these minerals are characteristic of 

 the district. The most typical combination in the material mined 

 is quartz, limonite, and barite. 



Sulfides 



The sulfides found are chalcopyrite, galena, marcasite, 

 pyrite, and sphalerite. 



Chalcopyrite. — A small amount of this mineral was noted in 

 a few localities in the district. A little was found at the Eye 

 mine on the North Fork of the Fourche a Renault and also at 

 the New Diggings south of Mineral Point. Considerable chal- 

 copyrite is found in some of the barite diggings in Morgan and 

 Cole Counties, especially where work is being done on veins. 



Galena. — Aside from the iron sulfides, galena, commonly 

 known in the district as "lead" or "mineral," is the most abund- 

 ant sulfide. It was discovered near Potosi and Old Mines about 

 1720 and has been mined more or less continuously ever since. 

 Some barite diggings do not contain any galena, but most of them 

 contain at least an occasional specimen. In fact the major part 

 of the district is covered with the old abandoned holes of the lead 

 mines. Occasionally the barite miners find as much as 100 



