PERIDOTE, a name applied by jewellers to the green transparent varieties of olivine. When yellow, or yellowish-green, the stone is generally known as “chrysolite.” The colour of the peridote is never vivid, like that of emerald, but is usually some shade of olive-, pistachio-, or leek-green. Although sometimes cut in rose-forms and en cabochon, the stone displays its colour most advantageously when it is worked in small steps. Unfortunately the peridote is the very softest of gem-stones, its hardness being only about 6 ’ 5, or but little above that of glass; hence the stone, when polished, rapidly loses its lustre, and readily suffers abrasion by wear. There is considerable difficulty in polishing the peridote; the final touch is given on a copper wheel moistened with sulphuric acid, yet, curiously enough, the mineral is soluble in this medium. The peridote is a silicate of magnesium and iron, having a specific gravity of about 3 - 4, and crystallizing in the orthorhombic system (see fig. 468, Mineralogy, vol. xvi. p. 410). Good crystals, however, are extremely rare, the mineral being usually found as rolled fragments. The localities for peridote and chrysolite are Egypt, Ceylon, Pegu, and Brazil, while the dull varieties of olivine enjoy a world-wide distribution in various eruptive rocks and in serpentine. Olivine is found also in meteorites....