Minerals and Metals in Ancient India v2.c43.s3.t8.1

v2.c43.s3.t8.1

Before we narrate the Sanskrit nomenclatures, let us briefly mention the modern scientific definitions of the chalcedony group of minerals. Common chalcedony is hydrated silica of faint unifom colour, low hardness (6-1/2), low specific gravity (2.60), somewhat porous and consisting of very thin layers of hydrated and cryptocrystalline silica. When such layers are prominent and concentric or wavy, the material is known as agate. When the bands are plain, parallel and alternately light and dark, the variety is called onyx.