THE BARITE DEPOSITS OF MISSOURI 65 



very irregular shape and outline (PI. IV. C) and in the same 

 beds as the veins, altho it is not directly connected with them. 

 The barite either fills the numerous small cavities which are so 

 abundant in the Potosi and the Proctor formations or it replaces 

 the dolomites. In both formations the disseminated barite is 

 much more abundant near the larger veins. Because the small 

 openings in the dolomites are so numerous, it is probable that 

 these furnished the location for the deposition of the barite, but 

 doubtless many were enlarged by the solutions and replacement 

 deposits were produced. The distribution of the disseminated 

 barite is almost identical with that of the veins, and from this it 

 is to be inferred that these types of barite deposit are genetically 

 connected. 



Cave deposits 



The presence of solution cavities in the Potosi and Proctor 

 has been mentioned in the descriptions of these formations. In 

 addition to these cavities which are filled with sandstone and 

 conglomerate, there are some which are more or less filled with 

 barite, calcite, and minor amounts of sulfides. Such cavities 

 occur in the Central district in considerable numbers. 



Very little information was to be had about these caves be- 

 cause only a small portion of any given one was exposed. The 

 socalled "circle" near Henley, Missouri, is a cave deposit of ex- 

 ceptional size. The open cut is now about 250 by 285 feet and at 

 the steepest face about 30 feet high. The barite generally fills 

 in the openings between large blocks of dolomite which lie at all 

 angles to the bedding planes on the sides of the cave. These 

 blocks are roughly cubical and may be 15 to 20 feet on a side. 

 Partially filled openings contain a deep, extraordinarily plastic 

 clay of a chocolate brown color, in which occur tabular crystals 

 of barite weighing several pounds each. These crystals also are 

 in large clusters weighing 200 to 300 pounds. The barite here is 

 pure white and very free from iron. It occurs in masses up to 

 ten inches thick and several feet long. (PI. VIII, A and B). 

 Veins of barite dipping 60° or more occur along the sides of the 

 cave. They represent cracks developed around the circle by the 

 caving in of the top. While there may be a good many of these 

 caves in the Washington County district only a few of them were 



