CHRYSOPRASE , a name applied by modern mineralogists to an apple-green variety of chalcedony or hornstone, used as an ornamental stone. The colour is due to the presence of nickel, probably in the form of a hydrous silicate. By exposure to a moderate heat, or to strong light, the chrysoprase becomes paler, or even colourless, but it may regain its colour by absorption of moisture. Chrysoprase is a mineral of rather limited distribution. Most of it comes from the neighbourhood of Frankenstein in Silesia, where it occurs in association with altered serpentine. It is found to a limited extent at Revdinsk, near Ekaterinburg, in the Urals; and it occurs also in India. It is known, too, at several localities in North America, notably at Nickel Mount, Douglas county, Oregon, where it occurs in nickeliferous serpentine.
The chrysoprase of the moderns is certainly not the chrysoprasius of Pliny, or the of Greek writers. The ancient stone was not improbably our chrysoberyl, and it is doubtful whether the modern chrysoprase was known until a comparatively late period. The chrysoprase of Kosemütz, near Frankenstein in Silesia, was discovered in 1740, and used by Frederick the Great in the decoration of the palace of Sans Souci at Potsdam. But at a much earlier date the Silesian chrysoprase was used for mural decoration at the Wenzel chapel at Prague. Chrysoprase was a favourite stone in England at the beginning of the 19th century, being set round with small brilliants and used for brooches and rings. At the present time it is said to be regarded by some as a "lucky stone." Much commercial chrysoprase is chalcedony artificially stained by impregnation with a green salt of nickel.
(F. W. R.*)
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)