Black and Green Moss Agate ,Sea found hand polished with inclusions of rust .880 gr weight. Ideal for Home Deco ,crafts ,sculpting mosaic cabochon making ,stone setting . Moss agate is a semi-precious gemstone formed from silicon dioxide. It is a form of chalcedony which includes minerals of a green color embedded in the stone, forming filaments and other patterns suggestive of moss. The field is a clear or milky-white quartz, and the included minerals are mainly oxides of manganese or iron. It is not a true form of agate, because it does not have concentric banding.