'black-jack' definitions:

Definition of 'black-jack'

From: GCIDE

Sphalerite \Sphal"er*ite\, n. [Gr. ??? slippery, uncertain. See Blende.] (Min.) Zinc sulphide; -- called also blende, black-jack, {false galena}, etc. See Blende (a) . [1913 Webster]

From: GCIDE

Blende \Blende\, n. [G., fr. blenden to blind, dazzle, deceive, fr. blind blind. So called either in allusion to its dazzling luster; or (Dana) because, though often resembling galena, it yields no lead. Cf. Sphalerite.] (Min.) (a) A mineral, called also sphalerite, and by miners {mock lead}, false galena, and black-jack. It is a zinc sulphide, but often contains some iron. Its color is usually yellow, brown, or black, and its luster resinous. (b) A general term for some minerals, chiefly metallic sulphides which have a somewhat brilliant but nonmetallic luster. [1913 Webster]