Vintage stone ashtray with orthoceras fossils

Vintage ashtray in black stone with inlaid orthoceras fossils. Consisting of a polished plate, with a hollow in its center, triangular in shape. One of the corners has a natural breakage with polished edges as well. The stone plate includes orthoceras, or white mollusc fossils, as well as reddish "spots" probably from iron extracts... Good general condition, original breakages. Length 18 cm, width 12 cm, thickness 1.8 cm.