The formation methods are different: black agate is a kind of agate in nature, which is extracted from jade; Obsidian is a natural colored glass formed by the sudden cooling of magma from volcanic lava.

Different transparency: under strong light, obsidian will appear brown light; Black agate hardly passes through under strong light.

Different hardness: the hardness of black agate is as high as 7 and the specific gravity is 2.6; The hardness of obsidian is between 5.6 and 6.2, and its specific gravity is 2.55.