MINERAL COMPOSITIONS AND TEXTURES OF JADEITE JADE AND THEIR RELATIONSHIPS TO QUALITY TYPES

The present paper studies 18 specimens in detail and summarizes the relationship of textures and minerals to the quality type. The jadeite jade specimens studied in the present paper are composed of main jadeite and omphacite (in only one specimen) and minor feldspar and some opaque minerals. These jadeite jade specimens show mainly following texture types: granular crystalloblastic texture, equigranular crystalloblastic texture, inequigranular crystalloblastic texture, prismatic crystalloblastic texture, fibrous crystalloblastic texture, mortar texture, mylonitic texture, fractured texture, and some textures formed by replacing. The quality of the studied jadeite jade specimens are closely related to the mineral compositions and textures. High quality jadeite jade specimens with high transparency, such as oily mass green jade and icy jade, were formed by later geological processes, such as recrystallization, or replacing, and show fibrous crystalloblastic texture, micro granular crystalloblastic texture. Moderate quality jadeite jade specimens have slightly been influenced by later geological processes, and often show fine granular crystalloblastic texture and mortar texture. The low quality jadeite jade specimens with low transparency, such as applegreen jade, have not been influenced by later geological processes, and mostly show inequigranular crystalloblastic texture, moderate granular crystalloblastic texture, prismatic crystalloblastic texture, and fractured texture. In all specimens with green veins, spots and masses, the green parts have micro granular texture of fibrous texture. On the other hand, if the texture is similar, the more pure the mineral composition of a jadeite jade specimen is, the higher the quality type of the jadeite jade specimen is. The jadeite jade specimens with other associated minerals, such as feldspar and some opaque minerals, are often poor in quality.