By the latest scientific standards, jade is divided into two categories: solid and soft. The former is a kind of hornblende with a rigidity of 6-6.5 degree while the latter is a kind of augite with a rigidity of 6.5-7, higher than that of glass. The so-called ¡°antique jade¡± is soft jade, which was called ¡°warm jade¡± in the past because its color and texture are warm and mild. ¡°Cold jade¡± is aquatic jade or ice solid jade, which is as clear and ice-cold as crystal.

In terms of luster, jade falls into the following categories, white jade, sapphire, topaz, gray jade, black jade, green white jade, gray yellow jade, gray white jade and others. However, the current categorization on the market is rather ambiguous and vague. As a result, luster of jade is hard to tell since there are no standards to measure against. Thus, most people can only tell white jade, sapphire, topaz, gray jade and black jade. Only after mastering considerable knowledge about jade luster can you tell the rest. Based on the sources jade is divided into three categories: jade mined in the mountains, waters and sands.

• Jade mined in the mountains: The mines are widely dispersed among the mountains and are the major source of large blocks of jade.
• Jade mined in the waters: the mines appear in small patches. And the surface of the uncut jade always looks filemot. It is of the best quality among all sorts of jade.
• Jade mined in the sands: Mined on the dry riverbed, it is similar in texture to jade mined in the waters.

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