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roof shale
The layer or seam of shale occurring immediately above the Pittsburgh coal seam. Because of its friable nature, this shale or slate is taken down in most mining operations.
- 词性: noun
- 行业/领域: 采矿
- 类别 一般矿业; Mineral mining
- Government Agency: USBM
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创建者
- ed.young
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(Milwaukee, United States)