What is "bituminous limestone"

Bituminous \Bi*tu"mi*nous\, a. [L. bituminosus: cf. F. bitumineux.] Having the qualities of bitumen; compounded with bitumen; containing bitumen.

Near that bituminous lake where Sodom flamed.
--Milton.

Bituminous coal, a kind of coal which yields, when heated, a considerable amount of volatile bituminous matter. It burns with a yellow smoky flame.

Bituminous limestone, a mineral of a brown or black color, emitting an unpleasant smell when rubbed. That of Dalmatia is so charged with bitumen that it may be cut like soap.

Bituminous shale, an argillaceous shale impregnated with bitumen, often accompanying coal.

Bituminous limestone is limestone impregnated and sometimes deeply colored with bituminous matter derived from the decomposition of animal and plant remains entombed within the mass or in its vicinity.