Jade , a beautiful material, whose physical characters have not yet been determined, though this stone was known to the remotest antiquity, and employed in the extreme East. It scratches glass, emits sparks when struck by steel, and is very difficult to break. It has the transparency of white wax, and when polished presents a certain fatty or oily appearance. The colour passes from white to olive green, and a very choice and highly valued variety is of a brighter green, almost emerald in some parts and nearly transparent. This species is known as imperial jade. In the Middle Ages, it was known in the West only as a sort of talisman, as a remedy for, or protection against, nephritic diseases, whence its name.

Antique Sardonyx Vase, mounted in enamelled gold work of the Henry II. period. (Louvre.).