A141 Green Onyx

A chalcedony that occurs in bands of different colors and is used as a gemstone, especially in cameos and intaglios. A variety of quartz, closely allied to agate, characterized by a structure in parallel bands differing in color or in degree of translucency: in the better kinds the layers are sharply defined and the colors white with black, brown, or red. Measures 29x25mm.