Chrome Greens, commonly so called, are compound pigments, of which chrome yellow is the principal colouring substance. These are also called Brunswick green, etc. and are compounds of chromate of lead with Prussian and other blue colours, constituting fine greens to the eye, suitable to some of the ordinary purposes of mechanic art; but for obvious reasons before given are unfit for fine art. See Chrome Yellow. There is, however, a true chrome green, or Native green, the colouring matter of which is the pure oxide of chrome; and, being free from lead, is durable both against the action of the sun's light and impure air. It is of various degrees of transparency or opacity, and of several hues more or less warm or cool, which are all rather fine than brilliant greens, and afford pure natural and durable tints. Trite Chrome greens neither give nor receive injury from other pigments, and are eligible for either water or oil painting, in the latter of which they usually dry well. They afford valuable colours also in enamel painting. The green of the Definitive Scale, p. 39, is of this latter kind, and as it is the only transparent green which can be used in oil, and is of a natural colour and perfect durability, it is a valuable acquisition to the oil painter especially in landscape. In water it requires much gum. To this substance it is that the emerald owes its green colour.