JARGON, a kind of precious stone, of the nature of the diamond, but softer; found in Brasil according to M. de Bomare; but in Ceylon, according to M. Rome de L'Isle. Its specific gravity is nearly equal to that of the ponderous spar, being 44.16. Its crystals consist of two tetrahedral pyramids of equal sides, separated by a short prism; so that the jargon is properly of a dodecahedral form. According to some lapidaries, the jargon comes nearest to the sapphire in hardness; and as they have when cut and polished a great resemblance to the diamond, they are also called by some soft diamonds; and one may be easily imposed upon in purchasing these for the true kind, when they are made up in any sort of jewellery work. On exposing this stone to a violent fire, M. D'Arcot found the surface a little vitrified where it stuck to the porcelain test in which it was set; whence it appears, that the jargon has not the least resemblance to the diamond, which is destructible by fire. See DIAMOND.