Jadeite
Jadeite is one of a group of minerals known as pyroxenes. Basically it is a sodium aluminum silicate. One variety of it found in Central America has an intermediate composition between jadeite and diopside—a calcium magnesium silicate; it is usually referred to as diopside-jadeite. Still another variety, called chloromelanite, with a strong, dark-green-to-black color, has a composition intermediate between jadeite, diopside, and acmite—a sodium iron silicate. Whether the sample is jadeite, diopside-jadeite, or chloromelaniie, all of these are unquestionably identifiable as pyroxenes and are close enough to jadeite to be recognized as merely slightly variant kinds of the same species.
The crystals of jadeite are not fibrous or matted, as are those of nephrite. However, they are complexly interlocked so as to have a compact, granular appearance. Jadeite, because of this difference, is not as tough as nephrite, but at 7 it is somewhat harder on the Mohs scale. It is measurably denser, too, than nephrite with a specific gravity varying from 3.30 to 3.36. Colors of jadeite tend to parallel those of nephrite, except that a pure-white or near-white jade is almost surely jadeite, as is a vivid emerald green 3 stone ring . Also reserved to jadeite are blue-greens, shades of lavender, and near red.
The challenge to the present-day jade carver and collector is an old one: how can jadeite and nephrite be distinguished from each other and from very similar substitutes? Most of the folklore of jade identification is worthless. For example, jade carvings do feel cool to the touch, as we are told, but so do many other stones. Simple tests can be applied, and long years of experience with jade can be used to make visual identification with a high percentage of success. In difficult cases, even among the experts, simple tests may fail miserably. Of course, there are more sophisticated methods available to the experts using expensive technical equipment and procedures that are just about foolproof.