54 UNIVERSITY OF MISSOURI STUDIES 



Relation to the wall roc/fe.— The vein material was deposited, 

 in part, directly on the walls of the fissure and, in part, it re- 

 places them. The veins are mainly filled fissures however, and 

 rarely replacements. The cavity walls were irregular, due to the 

 fact that they are often solution cavities. They are often lined 

 with crystals of dolomite which are continuous with and inter- 

 grown with the crystals of the dolomite of the country rock. The 

 cavities were in existence before the deposition of the barite and 

 other minerals and are not due to replacement. 



In a few instances a fault breccia cemented with barite was 

 observed. These breccias were original and the open spaces af- 

 forded a passage for the solutions which brought in the sub- 

 stances. Specimens showing casts of these angular fragments 

 are often seen. 



Geological distribution. — The veins are the most widely dis- 

 tributed geologically of any of the deposits, as they occur in all 

 the formations from the Potosi to the Jefferson City. They are 

 most abundant in the Potosi and the Proctor formations and the 

 Gasconade ranks next. They become less abundant in the higher 

 formations. If there were more, deposits in Morgan, Miller, and 

 Cole Counties, where the vein type predominates, the upper for- 

 mations, the Gasconade and Jefferson City, would be more im- 

 portant producers of barite. 



Areal distribution. — Little can be said as to the actual areal 

 distribution of the veins. Evidence was gathered which indi- 

 cates that they are essentially continuous with the areas where 

 residual barite is produced. In onty a few instances were the 

 larger veins seen, and then they were in the areas of residual ba- 

 rite. The smaller veins are very numerous and are in the same 

 areas as the larger ones, altho small sporadic veins may be seen 

 almost anywhere in the upper part of the Potosi. 



Value. — Only a small production is made from the veins, 

 because of the difficulty and cost in mining. They will become 

 more important as the residual deposits are exhausted. 



Disseminated barite 



Barite is widely scattered thruout the Potosi formation and 

 to a certain extent the Proctor also. It occurs as small masses of 



