About the History and Properties of Peridots

Hybrids are foreign to mineralogy, but there is no precious stone so difficult to specifically determine as chrysolite, because of the confusion regarding it in the minds of those engaged in the commerce of precious stones.

Mineralogists generalize the varieties of chrysolite under the common term "olivine." To American jewellers it is perhaps most commonly known as peridot. With the usual indifference to mineralogical distinctions of the average jeweller, it is possible that more green garnets than chrysolite are sold under the name olivine. W. R. Cattelle, in his book, Precious Stones writes:

The distinction between varieties is practically one of colour only. For many years lapidaries were in the habit of calling the chrysoberyl "Oriental chrysolite," and in consequence the two stones have been confused, though the chrysolite is much the softer stone and usually shows marked differences in colour and lustre.

At present it is customary to call those which incline most to yellow "chrysolite"; the yellowish green, resembling a light tourmaline with a dash of yellow, is known by the name "peridot," given to it by the French jewellers; and "olivine" is the name associated with the brighter yellowish emerald-green variety, although originally the yellow to olive-green stones were known by that name.

Few olivines are sold as such. The beautiful bright yellowish-green stones known here as olivines, are generally demantoids, Russian green garnets, of about the same hardness; these are rarely found large enough to cut to gems of over one half to three quarters of a carat.

Olivine crystallises in the orthorhombic system; also occurring massive; compact or granular; usually in embedded grains; hardness, 6.5 to 7; specific gravity, 3.33 to 3.44; cleavage, distinct; fracture, conchoidal; brittle; lustre, vitreous; colour, typical, olive green; brownish, greyish red and black. It is strongly doubly refractive with marked dichroism in some specimens; peridot showing straw-green and a green image. Gem kinds and their colours are chrysolite, yellowish green; peridot or "evening emerald," olive pistachio, or leek-green colour, of a hue more subdued than the emerald--green beryl. The approved tint of peridot resembles that revealed by looking through a delicate translucent green leaf. Hyalosiderite, "Job's tears," is highly ferruginous variety; specific gravity attaining 3.57; colour, a rich olive green.

Olivine is a frequently occurring constituent of some eruptive rocks, is also found in granular limestone and dolomite, and in several schists and ore deposits. Chemically, olivine--a sample specimen--is composed of, approximately, silica, 41; magnesia, 50; iron oxide, 9.