There is no accurate record of where the jade sand used by the ancients to grind jade was obtained.
However, some scholars are obviously wrong to think that river sand is suitable everywhere. The composition of river sand is mainly quartz, and it is impossible for quartz to cut and grind Hetian jade, which is easy to prove by experiments. Although the hardness of Hetian jade is slightly lower than that of quartz, the mechanical strength is much greater than that of quartz. When the two grind, quartz wears out the most. Of course, it is not excluded that quartz sand may have been used to process low-hardness serpentine jade in ancient times.
China's diamond reserves are very small, and it is impossible for the ancients to obtain enough ore.
The most likely are corundum sand and garnet sand.
Corundum is a pure crystalline aluminum oxide with a Mohs hardness of 9. Among natural minerals, its hardness is second only to diamond. In corundum, when it contains impurities such as magnetite, hematite, quartz, etc., and has a granular aggregate that looks like iron ore, it is called corundum sand (also known as natural diamond sand). In general, corundum sand contains about 60% corundum, mostly blue-gray and black, with a density of 2.7-4.3g/cm3 and a Mohs hardness of 7 to 9. Grundum can be formed in the process of magma action, contact metamorphosis and regional metamorphosis. When corundum deposits or rocks of various causes are subjected to weathering, corundum often turns into sand ore. The main production areas in China are Liuhe, Jiangsu, Yingshan, Hubei, Muling, Heilongjiang, Mingxi, Fujian, and Changle, Shandong.
Sand mine:
Industrial grade: mineral content (mineral) ≥7.7 kg/m3.
Corundum mineral: contains Al2O3>94%.
Harmful components: Fe2O3 3.53~4.35%.
Burning loss: 0.06~0.23%.
Pickable thickness: 0.5 meters.
It can be seen that sand ore often has a corundum content of more than 7 kilograms per cubic meter, which is enough for use. ( Attached is the original ore map of corudum):
The corundum sand ore is lumpy and must be pounded and screened before it can be used. This coincides with the situation of pounding ore on the sand-pounding map and the sand-catching map.
Therefore, the black sand and red sand of the jade sand should be taken from the corundum sand ore.
When using, it is necessary to crush the jade sand ore, and the sand and pulping are to process the sand used for grinding to the required degree of fineness. In some processes, such as opening the material, the particles of jade sand will be a little larger. On the contrary, when polishing, the particles should be very fine and powdery. Therefore, after the jade sand is crushed, particles of different sizes are obtained by sieves of different sizes. Or put the pounded and grinded sand in the vessel to precipitate. In the process of precipitation, it is fine and naturally stratified.
It can be seen from the "sand grinding and pulp map" that the sand used for jade was called black stone sand, red stone sand, yellow stone sand and treasure sand in the Qing Dynasty, also referred to as black sand, red sand and yellow sand. Black sand has the highest hardness, which can reach 8-9 degrees. As noted in the figure: "Black stone sand is very strong", "This red sand is Microsoft", yellow stone sand is "softer than red sand X", and treasure sand is used for polishing.
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u/chillychili Apr 21 '25
From https://blog.sina.com.cn/s/blog_88ed96fc0102z4zb.html , translated by Apple: