What is the meaning of Black-jack?

Sphalerite; zincblende.

Caramel or burnt sugar, used to colour wines, spirits, ground coffee, etc.

A large leather vessel for beer, etc.

A water oak or barren oak (Quercus nigra).

A native African longshoreman or sailor working on a boat.

A coalfish (Pollachius virens).

A larva of a sawfly of species Athalia rosae (syns. Athalia centifolia, A. spinarum).

Source: wiktionary.org