Though not usually accounted precious among European nations or in Western civilization in general, jade was held in extraordinary esteem by primitive man, and was fashioned by him into ornaments and utensils, often of considerable beauty, and even at the present day it ranks among the Chinese and Japanese peoples above all precious stones; indeed, the Chinese word _Yu_ and the Japanese words _Giyuku_ or _Tama_ signify both jade and precious stones in general. According to the Chinese, jade is the prototype of all gems, and unites in itself the five cardinal virtues—_Jin_, charity; _Gi_, modesty; _Yu_, courage; _Ketsu_, justice; and _Chi_, wisdom. When powdered and mixed with water, it is supposed to be a powerful remedy for all kinds of internal disorders, to strengthen the frame and prevent fatigue, to prolong life, and, if taken in sufficient quantity just before death, to prevent decomposition. Jade is a general term that includes properly two distinct mineral species, nephrite or greenstone, and jadeite, which are very similar in appearance, both being fibrous and tough in texture, and more or less greenish in colour; but it is also applied to other species such as saussurite, californite, bowenite, and plasma, which have somewhat similar characters. The word jade is a corruption of the Spanish _pietra di hijada_, kidney-stone, in allusion to its supposed efficacy in diseases of that organ. Nephrite or greenstone (Plate XXIX, Fig. 16) is the commoner of the two jades. It is closely allied to the mineral hornblende, a silicate of magnesium, iron, and calcium corresponding to the formula Ca(Mg,Fe)_{3}(SiO_{3})_{4}, the magnesia being replaceable by ferrous oxide. Microscopic examination shows that the structure consists of innumerable independent fibres foliated or matted together, the former character giving rise to a slaty and the latter to a horny appearance in the stone as seen by the unaided eye. The colour varies from grey to leaf- and dark-green, the tint deepening as the relative amount of iron in the composition increases, and brown tints result from the oxidation of the iron along cracks in the stone. The hardness is 6½ on Mohs’s scale; nephrite is therefore about as hard as ordinary glass and softer than quartz. When polished, it always acquires a greasy lustre. The specific gravity ranges from 2·9 to 3·1. The least and greatest of the principal refractive indices are 1·606 and 1·632 respectively, the double refraction being biaxial and negative; the coloured fibres also display dichroism. All these differential effects are, however, masked in the stone because of the irregularity of the aggregation. Nephrite is fusible before the blowpipe, but only with difficulty. Its name is derived from the Greek word νεφρός, kidney, the allusion being the same as for jade.