SARDONYX.                                 287
	This name is of later date than Theophrastus, by whom the stone was included (if indeed then known) amongst the varieties of the ïííãéïí. It is defined by Pliny as originally signifying a white mark in a Sard (candor in Sarda) like the human nail placed upon flesh, and both of them transparent.* Such was the true Indian sort, according to Ismenias, Domostratus, Zenothemis, and So-tacus. The two last writers call the opaque stone of this class " The Blind Sardonyx;" to such in Pliny's age was the name exclusively confined (qua? nunc abstulere nomen). The Arabian kind exhibited no traces of the Sard (i. e. of a transparent red layer), and admitted of a variety of colours ; the base (radix), black or verging on blue ; the surface (unguis), like vermilion, encircled by (redimitus) an opaque, fatty, white layer (intermediate), and passing into the white with a slight tinge of purple (or blue). And more tersely and intelligibly Solinus : "In the Arabian Sardonyx the surface is admired if of a purer red ; but found fault with, if of a dirty tint : the middle is girt by an opaque white line. The best is where neither layer diffuses its colour upon its neighbour, nor borrows any­thing from the other, and the last (the base) finishes off with * The French mineralogists still continue to distinguish this from the Sard-Onyx, by giving it the name of Sard-Agate. The upper layer 'in -which the designs are usually relieved) is a true, transparent, red Sard ; the ground an equally transparent White Agate.