The New International Encyclopædia/Horse (miner's term)

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HORSE. A miner's term, applied to any intruded material which is the apparent cause of a sudden interruption in the continuity of a mineral that is being quarried, as when a dike of igneous rock cuts across an ore body. In vein-mining a detached mass of rock or spar which fills the vein is called a horse, while colliers apply the term to the shale which replaces the coal-bed, as well as to such interruptions as seem to have been the channels of small streams, and which were subsequently filled up by the clay that formed the roof of the coal.