Pearl hardness grade

The hardness of a pearl is mainly determined by the type of minerals that make up the pearl, and is generally about 2.5 to 4.5, which is a relatively hard substance. The thicker the nacre, the better the quality and the higher the hardness. In pearls, the tiny crystals of vermiculite are closely combined with the shell keratin, so that the pearl exhibits a hardness of 3, and the hardness of the vermiculite that constitutes the pearl is 3.5-4. Gao Gangqi [1955] uses the Pisch method to measure the pearl hardness. 3.5-4.5. These indicate that the pearl is a relatively hard substance, and the more the number of pearl coating layers, the greater the hardness. The hardness of pearls is harder than copper, silver, gold, calcium, magnesium, lead, potassium and sodium, but not as good as diamond, chromium, tungsten, nickel, etc., and the hardness of iron is not far behind. The higher the hardness, the better the pearl; at the same time, the hardness of the pearl is proportional to the particle size of the pearl, that is, the particle is large, and its hardness value is relatively high, but it seems to have nothing to do with the color of the pearl. Only the hardness of fine pearls is higher than copper and close to iron. The hardness of the hardness of the pearl is measured by a durometer. Minerals and gemstones were measured using a Mohs hardness tester according to the following criteria.

1 degree: talc, easy to break with nails.

2 degrees: gypsum or calcium sulfate, with nails can slightly damage.

3 degrees: calcite, the knife is easy to destroy.

4 degrees: fluorite, a knife can slightly damage.

5 degrees: apatite, steel can not rub, can be contused.

6 degrees: feldspar, steel friction can spark.

7 degrees: Quartz, steel friction is prone to sparks.

8 degrees: Huang Jing, the sickle does not move.

9 degrees: corundum, can not be damaged outside the diamond.

10 degrees: diamond.