This is the most popular of the opaque green stones, and the rarity of fine colored specimens makes it the most expensive of the opaque gem materials. Its pleasing color and hardness render it suitable for most articles of jewelry that are worn, and the differ­ent shades of green with which we usually associate jade harmonize well with a number of other colors.

As a gem stone, however, its finer appreciation is very limited in Western countries, and we have to turn to the East, and par­ticularly to China, in order to observe with what care and exacti­tude this stone is considered. For in China, no other stone is re­garded with so much reverence; it is of such importance that it is considered as being precious and ranking above all other stones, including the diamond. In the East, it is connected with ancient traditions and customs, and its use dates back to many centuries. In the West, it was little used until the last century, and its gen­eral popularity still varies with fashion.

Actually, the term "jade" includes two distinct types of stones, although they have some properties in common. These are jadeite, more commonly known as Chinese jade, and nephrite, which is more generally called New Zealand jade, Greenstone, or Maori Stone. Both types belong to the monoclinic system of crystalog-raphy and both are generally found in massive form, boulders, waterworn pebbles, and not as crystals. Each is characteristically green in color, although the shades of green are different. Jadeite is a pyroxene, and nephrite belongs to the amphibole or horn­blende group of minerals. They are different in chemical com­position and in many physical properties. Yet they are generally considered under the one heading of Jade.

By far the rarer of the two varieties is jadeite, which was first distinguished chemically and so named in the year 1863. It is a silicate of sodium and aluminum with some traces of other metals, particularly calcium, magnesium, iron, chromium, and manga­nese. These give the colors to the material, and although green is the predominant shade, mauve, violet, pale blue, orange, red, and yellow jadeite are found. These unusual colors are, however, usually rather pale and less definite than the greens. The fine green color is probably due to chromium; the best qualities are translucent and not opaque, and white patches, variations of color, and surface cracks should be absent.