Group of 3 worked obsidian fragments and a raw obsidian lump, Neolithic or later, 5th millennium or later, Cycladic, Obsidian, a: 13/16 ? 1 7/8 ? 3/16 in. (2.1 ? 4.8 ? 0.5 cm), Miscellaneous-Stone, Obsidian is a natural glass. The lump of obsidian is