Microscopically the ores are medium grained to amorphous.
显微镜下，矿石为中粒至非晶质。
Pores are closely correlated with sandstone fabric, and are more easily generated in medium grained sandstone where feldspar content is high(>37%) and cement content is low(carbonate<50%).
孔隙与砂岩组构密切相关，孔隙更容易产生于长石含量高（>37% ）、且胶结物含量低（碳酸盐<5 % ）的中粒砂岩中。
In the part of west flank of Lujiatuo minefield, the normal siltstone roof of coal seam 8 changed into coarse to medium-grained sandstone, and also had phenomenon of coal seam pinch-out.
吕家坨井田西翼部分区域八煤层顶板由正常的粉砂岩变为粗中砂岩，并有煤层变薄现象。
In the part of west flank of Lujiatuo minefield, the normal siltstone roof of coal seam 8 changed into coarse to medium-grained sandstone, and also had phenomenon of coal seam pinch-out.
吕家坨井田西翼部分区域八煤层顶板由正常的粉砂岩变为粗中砂岩，并有煤层变薄现象。
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