Lapis nephriticus, or Jaspachates, a genus of siliceous earths. It gives fire with steel, and is semitransparent like flint. It does not harden in the fire, but melts in the focus of a burning glass into a transparent green glass with some bubbles. A kind brought from the river of the Amazons in America, and called circumcision stone, melts more easily in the focus into a brown opaque glass, far less hard than the stone itself. The jade-stone is unctuous to the touch; whence Mr Kirwan seems to suspect, that it contains a portion of argillaceous earth, or rather magnesia. The specific gravity is from 2.970 to 3.389; the texture granular, with a greasy look, but exceedingly hard, being superior in this respect even to quartz itself. It is infusible in the fire, nor can it be dissolved in acids without a particular management; though M. Sauvage seems to have extracted iron from it. Sometimes it is met with of a whitish milky colour from China; but mostly of a deep or pale-green from America. The common lapis nephriticus is of a grey, yellowish, or olive colour. It has its name from a supposition of its being capable of giving ease in nephritic pains, by being applied externally to the loins. It may be distinguished from all other stones by its hardness, semifluidity, and specific gravity.