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data indicate that , at times , the coal rests directly on the <br /> sandstone . Generally , however , it is found interbedded with <br /> shales and siltstone up to 13 ' above the Rollins . <br /> The coal interval consists of various coal <br /> seams and partings which total 20 ' to 30 ' thickness . A <br /> lower seam has been identified as the "A" bed , but is not <br /> mired . Above it is the "B" Bed , also known as the Coal <br /> Basin Seam, from which coal is mined through Mine entry <br /> Nos . 1 , 3 , 4 , and 5 . The "B" Bed ranges from six to nine <br /> feet thick. Occasionally , it converges with the "A" seam, <br /> but for the most part , the two seams are widely separated by <br /> as much as 39 feet of rock. <br /> Within the overlieing Williams formation, two <br /> sandstone members , known as the Middle and upper Sandstone <br /> members , separate thick shale formations . Above the sandstone <br /> members lie coal beds . <br /> Above the Rollins formation and the "B" bed <br /> coal seam is a thick layer of mudstones , sandstones and <br /> shales of 370 ' to 425 ' thickness , known as the Lower Bowie <br /> Shale Submember . Bowie Shale occurs in the Williams Fork <br /> formation. <br /> The Middle Sandstone Submember overlies the <br /> Lower Bowie Shale and is similar in man;; respects to the <br /> Rollins Sandstone . It ranges in thickness from 30 ' to 130 ' <br /> and is fire-to-medium-grained , quartzitic to feldspathic , <br /> 9 <br />