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black bat
A piece of bituminous shale embedded in the rock immediately over the coal measure and liable to fall of its own weight when the coal beneath it has been removed. Compare: kettle bottom
- 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)