or CHRYSOPRASUS, the 10th of the precious stones mentioned in the Revelations, as The chrysopeir is by mineralogists reckoned to be a variety of the chrysolite, and by Cronstedt called the yellowish green and cloudy topaze. He conjectures that it may perhaps be the substance which serves as a matrix to the chrysolite; as those that he had seen were like the clear veined quartz, called in Sweden milk crystal, which is the first degree of crystallization.

The chrysopeir, according to M. Magellan, is of a green colour, deeper than the chrysolite, but with a yellowish tinge inclining to blue like the green leek. M. Achard says that it is never found crystallized, and that it is semitransparent. By others it is reckoned among the quartz, and its colour is supposed to be owing to the mixture of cobalt, as it gives a fine blue glass when melted with borax, or with fixed alkali. Mr Achard, however, found the glass of a deep yellow when the fusion was made with borax; and that it really contains some calx of copper instead of cobalt. Mr Dutens says, that some gold has been found in this kind of flake; but this last belongs in all probability, says M. Magellan, to another class of substances, viz. the vitreous spars.

To the latter belongs most probably the aventurine, whose colour is generally a yellow-brown red; though sometimes it inclines more to the yellow, or greenish, than to the red. These stones are not quite transparent; some indeed shine with such a brilliancy, as to render them of considerable value, but they are very rare. The common aventurine is but an artificial glass of various colours, with which powder of gold has been mixed; and these imitated aventurines so frequently excel the native ones in splendor, that the esteem of the latter is now much lowered. With regard to the chrysopeir, its name from χρυσός shows it to be of a greenish-blue colour, like the leaves of a leek; it only differs from the chrysolite in its bluish hue.