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a. A name for zinc ore; blackjack. See: sphaleriteb. Cannel coal interstratified with shale.
c. Coaly shale, commonly canneloid.
d. To drill a rock by hand, using a 4-lb (1.8-kg) hammer in one hand and a
steel drill in the other ("single jacking"). "Double jacking" is to use a
two-handed (sledge) hammer with the steel drill held by another worker.
e. A portable device used for exerting great pressure or for lifting a
heavy body through a small distance. Syn: anchor jack
Source:
Dictionary of Mining, Mineral, and Related Terms
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