Obsidian is a semi-precious gemstone surface — a Deep jet-black obsidian gemstone slab — large angular obsidian fragments set in a mosaic, separated by thin pale gold​/​white seams that map the broken edges. Glassy, gem-like depth typical of a backlit semi-precious panel. slab with a polished finish, often backlit as a feature panel, vanity or bar front. A dramatic decorative stone for interior feature applications.