Ina Quadrangle

Mining in the Ina Quadrangle

The Rend Lake Fault System impacted the mines in the Ina Quadrangle, with individual faults causing displacement up to 13 feet. In some areas, expansion was halted because of the faults and in other areas, the faults could be accommodated by altering the mine plan. The poor roof conditions were a more continuous problem. Thick Energy Shale required a great deal of support and often came down in spite of the additional support. The shale was composed of thin laminations interspersed with carbonaceous and sandy layers that did not adhere well to each other. Top coal was often left to support the roof. In some areas, a silty gray shale made the immediate roof, and this was even more difficult to support. Sometimes 2 feet of roof rock was taken down before roof bolts were installed. Rolls in the coal also contributed to roof difficulties. Some rolls were hundreds of feet long and tens of feet wide. The shale within the rolls did not adhere well to the layers above. Shear bodies were found in the Orient No. 6 Mine (mine index 885). The shear bodies probably formed as slumping features before the sediments solidified, and these occurred as lense-shaped masses. These shear bodies had low strength, and were particularly difficult to keep up. Roof falls of 30 feet above the coal were seen.

All of the mines that operated in the Ina Quadrangle worked for over 25 years. The coal was thick, as well as having a relatively low sulfur content (less than 2%).