Bales mine.-The Bales mine is 2 miles northeast of the Reeves mine. It consists of two sets of workings about one-fourth mile apart. One consists of a number of trenches, the other of a tunnel with shaft connection and several pits. Both workings are on the main ore-bearing layer above the Polk Bayou limestone. The ore is dark-blue, friable, and largely amorphous, and occurs in masses in umberous manganiferous clays, and as local replacements in the underlying limestone. Skinner-Abbot mine. The Skinner-Abbot mine is about 7 miles north-northwest of Batesville. The Izard limestone is here exposed abundantly at the surface. It has gone into solution along joint planes and formed openings with rounded vertical walls, from a few feet to 10 or 15 feet wide and ranging in length up to 100 feet. These openings contain black soil and brown and manganiferous clays that carry fragments of manganese ore. The ore is of three varieties: (1) Coarsely crystalline gray ore; (2) hard blue massive ore; and (3) hard blue porous finely crystalline ore. Roach mine.-The Roach mine is 9 miles north of Batesville. The workings consist of several trenches in clay, on a hill lying in a syncline of the St. Peter sandstone. No limestone is visible, but an abundance of chert fragments are scattered over the surface. The clay is darkbrown or chocolate colored and darkly stained by manganese. In some places it is so impregnated with manganese oxide as to form solid bodies of low-grade ore. Manganiferous clays alternate with masses of chocolate clays, and large bodies of chert breccia are found. with both. The chocolate clays contain kidney ore of hard blue massive psilomelane in irregular lumps 3 to 6 inches in length. Some of these are very closely packed together, and others are scattered at considerable intervals through the clay. The chert breccia consists of fragments of white chert cemented by a black amorphous manganese oxide that predominates over the chert. It occurs in large masses, some of them 4 or 5 feet in extent. The fragments of chert are generally small and considerable ore is found in the breccia masses in which there is little or no chert. Where cavities occur in the breccia ore they are lined with nodular projections. Much of the kidney ore contains chert fragments and thus grades into breccia ore. Baxter mine.-The Baxter mine, about one-half mile east of the Roach mine, consists of a large open cut. The walls are composed of reddish-chocolate clays below and lighter-colored clays with chert fragments near the surface. In the chocolate-colored clays are masses of dark-red decomposed shale and limestone. The ore is of a similar type to that in the Montgomery mine described below. Both the Baxter and the Montgomery cuts contain near their mouths large masses of a limestone-marble breccia. These are composed of a mixture of massive limestone like the Izard, and crystalline limestone like the lower part of the Polk Bayou. Montgomery mine.-The Montgomery mine adjoins the Baxter on the east and likewise consists of a large open cut. On the walls are exposed reddish-chocolate clays with large masses of dark-red decomposed limestone and shale, still showing original textures. The ore is of two kinds--pumaceous, finely crystalline ore and button-like, pebbly ore. The former occurs in thin parallel layers through the clay, as though it were a replacement of certain layers of rock. (See fig. 20.) Successive layers are varying distances apart and between them are residual clays. The button ore occurs FIGURE 20.-Sketch showing the occurrence of manganese ores at the Montgomery mine. in the clays as well as in the ore layers. It consists of small flattened and spherical pebbles, the former very much like those in the Cason mine. The flattened pebbles are seldom more than 11⁄2 inches in the longer diameter, and one-third inch thick, and the spherical pebbles are still smaller. The former lie with their longer diameters in the same plane, this probably being the plane of stratification of the original rock. Both types are dark blue. The button-like concretions are dense and hard; the ore layers, though hard, are porous. Meeker mine. The Meeker mine is about one-half mile west of Cushman. The workings consist of several open cuts and tunnels, mostly recent, on the manganese-bearing layer between the Polk Bayou limestone and the Boone chert. The surface of the former is very uneven, as in other places mentioned, and horses of it extend upward into the manganese-bearing layer. This varies from a few 37336°-Bull. 427-10-8 inches to 10 feet thick, depending on the size of the limestone horses. It is composed of the following succession of layers (fig. 21): Boone chert. Manganiferous clay 2 to 3 inches thick. Green shale varying in thickness up to a foot or more. Absent in places. Sandy manganese and iron oxide formation varying in thickness up to 6 feet FIGURE 21.-Sketch showing the occurrence of manganese ores at the Meeker mine. a, Boone chert; b, green shale or manganiferous clay; c, brown sandstone; d, manganese-bearing ferruginous shale; e, manganiferous clay or dark indurated siliceous layer; f, Polk Bayou limestone. The manganese-bearing layer consists of thin horizontal layers of manganese and iron oxides, mainly the former, interlaminated with yellow and red sandy material. The layers are generally crenulated and are one-sixteenth to one-half inch thick. The variations are generally abrupt and sharp, causing great irregularity. Locally large porous masses of manganese ore 4 or 5 inches thick are embedded in the low-grade laminated ore. They consist of dark-blue massive psilomelane, with a small amount of finely crystalline material in cavities. Many of the cavities are entirely or partly filled with calcite. Southern mine.-The Southern mine is about 1 mile north-northeast of Cushman. It consists of two large open cuts and many shafts. The Boone chert is exposed in the upper part of the cuts and beneath it are 10 to 15 feet of ocherous, manganiferous, red and brown clays, in which occur the ores. Many of the shafts go through 20 to 40 feet of chert into the underlying ore-bearing layer. The ore was not seen in place at the Southern mine. Grubb cut. The Grubb cut is several hundred yards northeast of the Southern mine. The workings consist of an old open cut with a recent shaft in the floor. The walls of the cut consist of Boone chert in the upper part with 10 to 15 feet of manganese-bearing clay below it. In the bottom there are horses of coarsely crystalline Polk Bayou limestone. The beds of chert are considerably folded as a result of slumping in the underlying clays. The ore recently taken from the shaft is of a hard blue porous variety of psilomelane, with some red ore which is presumably stained by iron. Polk-Southerd mine. The Polk-Southerd mine is about 2 miles northeast of Cushman and consists of an old cut and several old shafts. The chert forms the upper part of the walls of the cut, but the orebearing layer below it is covered with débris. Pieces of ore on the dump are of a porous blue variety of psilomelane. Turner mine.-The Turner mine consists of an old open cut and several shafts about half a mile northeast of the Polk-Southerd mine. In the bottom of the cut there are horses of massive blue Izard limestone with associated green shale. The manganese-bearing clay, which is reddish brown, lies directly on the Izard limestone, and is overlain by the Boone chert locally. The ore, consisting of massive blue psilomelane and gray crystalline braunite, is found in fragments in the clay. Many other old mines are present in different parts of the district, but those described show fully the different forms and associations in which the ores occur. ANALYSES. The following are analyses of psilomelane and braunite from the Batesville region: Analyses of psilomelane from the Batesville region.a a Penrose, R. A. F., jr., Manganese: Its use, ores, and deposits: Ann. Rept. Arkansas Geol. Survey for 1890, vol. 1, 1893, pp. 145, 147. |
