56 UNIVERSITY OF MISSOURI STUDIES 



found. The barite is deposited on the bottoms of the cavities, 

 and where the cavity is not completely filled there is an abund- 

 ance of crested forms. A globular mass 5 by 4 by 2 feet was ex- 

 posed in one of these caves near Cruise. How much more was 

 present is unknown. The order of deposition is the same as that 

 in the veins, viz., (1) quartz, (2) pyrite, (3) galena and sphaler- 

 ite (if present), and (4) barite. This invariable order over all 

 the district points to uniform conditions during the deposition of 

 the barite. None of the solution cavities seen, aside from the 

 caves, were very large and the majority were only a foot or two 

 across. They are not continuous along one plane but are nearly 

 horizontal for a few feet and then follow an inclined or vertical 

 passage to a lower horizontal plane. This is what would be ex- 

 pected in so uniform a rock as the Potosi or the Proctor dolo- 

 mite. Joints did not have a very important influence on the loca- 

 tion of the cavities. The presence of these solution cavities in 

 both the Proctor and the Potosi formations points to an uncon- 

 formity between the Proctor and the Gasconade, as well as be- 

 tween the Proctor and the Potosi. However, they might have 

 been developed much later, as such solution cavities occur in the 

 Jefferson City and other formations above the Proctor. 



Residual deposits of barite 



The residual type of occurrence is the most important type 

 of all and has been the most important since the mining of barite 

 began in Missouri, about 1870. This is because the barite is in 

 more concentrated form in the residual clays and because it is 

 also more easily extracted. 



Croppings. — It would be expected that a material which oc- 

 curs in surface clays would be exposed wherever the slope of 

 the surface was such as to permit the removal of much of the 

 associated clay. Such croppings are not numerous at the present 

 time in the areas that have been worked for barite for 30 or 40 

 years, but in the outlying districts, as for instance that on Hazel 

 Creek, on Wilson Creek (northwest of Potosi), and at Rich- 

 woods, the barite is found at the surface. In many fields on 

 slopes which have been tilled for 75 years or more, the barite has 

 been regarded as a nuisance, and has been more or less removed 



