McArthur mines, Potosi Barite Mining District, Washington County, Missouri, USAi

Regional Level Types
McArthur mines	Mine
Potosi Barite Mining District	Mining District
Washington County	County
Missouri	State
USA	Country

Under this title are included a number of mines upon some 10,000 acres of land, including several old Spanish and French grants. Mining was begun here in 1798 by Moses Austin on the well-known Mine a Burton tract, and since then has been carried on with greater or less diligence to the present day. The Castleman, Citadel and other old historic shafts are included in this property. One of the openings is described as follows by Mr. Robertson:

The Curtis and Hall shaft was formerly the old Willeke property. It is very near Potosi. The shaft was 32 ft. deep, in a close-grained , earthy, dove-colored limestone, containing cavities with small quartz crystals. The ore (galena) occurs in a succession of pockets in a stratum of limestone, at a depth of 30 to 32 ft.; the mineralized portions or channels are from 2 to 8 ft. in width and about a foot thick, sometimes increasing to 6 ft. This portion contains pockets filled with barite enclosing the lead ore, although the lead may occur in the limestone direct, with no barite gangue, but in this case in much smaller bodies. The usual occurrence is a body of barite lying horizontally about 4 feet wide and 6 inches to 1 foot in thickness, heavily mineralized with galena, which occurs both as more or less perfect crystals and as irregularly shaped masses. This ore body has generally a course about N. 20° W, but branches off in directions S. 60° E and S. 60° W. It is significant that these are the general directions of the jointage planes of the limestone. The galena is found in masses weighing from a few ounces to several hundred pounds. The barite occurs as the white opaque variety, often in masses stained yellow and black on the surface by iron and manganese, and covered with small tabular crystals. Calcite is often associated with the barite, crystalizing on it in compound scalenohedra.

In a shaft which was being sunk about one mile from the latter property, a distinct crevice was observed. The strike was nearly N.-S., and the crevice was about vertical. In was 2 to 6 inches wide, filled with barite and galena, lying in irregular masses in the barite. The wall rock was heavily bedded, siliceous magnesian limestone, and was apparently absolutely unaltered. No movement in the wall was perceptible. The crevice had been followed for about 60 feet in depth.

Austin, in writing of Mine a Burton in 1804, described the ore as found within 2 ft. of the surface. He separated it into two kinds: 1) "gravel mineral," found immediately under the soil, mixed with gravel and coated with cerussite, and extending into sand rock below; 2) mineral in a bed of red clay under the sand rock, in pieces from 10 to 500 lbs. in weight, associated with barite.

Schoolcraft, in 1819, described the ore as found in detached pieces and solid masses, in velns and beds, in red clay, accompanied by barite, calcite, pyrite and quartz. In the clay near the surface “radiated” quartz was found. The gravel ore occurred under 4 or 5 ft. of red clay, and consisted of fragments or “pebbles" of siliceous rock mixed with galena, the whole about a foot thick. At the New Diggings he reported that the most flattering velns were in view when water caused their abandonment. In the Austin shaft he speaks of large quantities of ore filling crevices in the rock.

Broadhead, describing this lead district in 1876 [31, p. 105], refers to the occurrence of galena in red clay at Mineral Point, and also of barite and galena in horizontal bands in limestone. He also mentions the finding of specimens of barite which had replaced galena, as is proven by the presence of right-angular galeniferous lines.