Emerald is a pyroxene type, monoclinic system, and two groups are completely cleavage. The main composition is sodium aluminum silicate NaAl9 (Si2O6), which contains more than 50% sodium aluminum silicate in gemstone ore, which is regarded as jadeite, and is produced in metamorphic rock formation formed under low temperature and high pressure. Often associated with blue amphibole, muscovite, hard pillar (dihydrate feldspar), vermiculite and quartz. The Mohs hardness is between 6.5 and 7, the specific gravity is between 3.25 and 3.35, and the melting point is between 900 and 1000 °C.
The early jadeite was not expensive, and its value was not high. It was not valued by the world. Ji Xiaotong (1724--1805) wrote in the "Notes on Reading the Cottage": "The weight of the cover is different from the fashion of the time. Also, when you remember the rest, ginseng, coral, lapis lazuli, the price is not expensive, today is the day .... Yunnan jade jade, at that time not to look at the jade, but as the blue field dry yellow, strong name to Yu ear, Today is a treasure, and the price is far from the real jade." According to "Shi Ya", the emerald stone weighing about 45 kilograms at the beginning of this century was worth eleven pounds. There is no shortage of essence in the jade stone, and the price is very expensive at that time, but compared with the one kilogram of jadeite in the early 21st century, it is almost a small witch. (According to: According to the record of Ouyang Xiu's "Return to the Field", at the latest in the early years of the Northern Song Dynasty, Jadeite was the name of the green treasure jade, which was forbidden in the treasure. Ji Xiaoyu said that it may be another jade.)
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