THE BARITE DEPOSITS OF MISSOURI 63 



and the mine located near a shipping-point. The barite under 

 these circumstances is to be considered as a gangue mineral. 



Crop pings. — There are few croppings of the barite veins be- 

 cause of the thick mantle rock in the region. They are generally 

 found in the bottoms of the streams or along very steep slopes 

 where there is very little, if any, soil. In neither instance are 

 they sufficiently exposed to permit an extensive, detailed study. 

 There are no surface features of importance on any of the crop- 

 pings ; the vein materials are merely uncovered by the streams. 

 On the slopes fairly good sections of the deposits may be seen. 



Character of the veins. — The veins are apparently not very 

 strong, altho they appear to be fairly extensive. Judging by the 

 extent of the residual deposits, they are persistent in length, and 

 appear to be quite numerous. How far down they extend is 

 unknown. There are many small veins, ranging from thin sheets 

 a few inches long up to two inches wide and ten feet long. 

 (PI. VII, B.) In some of the deeper mines of the region large 

 masses of barite are found associated with sphalerite or galena at 

 depths of 100 feet or more. 



Form and structure. — The veins are tabular but very irregu- 

 lar along their outcrop. In spite of their irregularities, they have 

 a persistent direction of strike, in general, nearly north and 

 south. A few veins varied as much as 45° from north. The 

 vein material extends from wall to wall and usually is massive. 

 Where quartz and pyrite or limonite are present, these minerals 

 are deposited in the above order on the walls and give that part 

 of the veins a banded appearance. Quartz alone may give a 

 banded character to the vein. The divergent masses of barite lie 

 at all angles. Cavities are of common occurrence in the veins 

 and are always lined with crested barite. (PI. IV, A.). When 

 sphalerite and galena are present they are either attached to the 

 walls or to the previously deposited quartz or pyrite. The barite 

 fills the remaining space. There are many branches shooting out 

 from the small veins into the dolomite. These show by their 

 irregular shape and relation to the wall rock that they are largely 

 replacements, the deposition of which probably began along fis- 

 sures and fractures of the rock. A noticeable feature is the nu- 

 merous small veinlets that are connected with these replacement 

 branches. 



