Generally, glass is between 2500 kg/m 3 and 3000 kg/m 3.
The artificial chronotropic crystal is a silicon dioxide crystal with a density of 2.65 and a hardness of 7.
The density of crystal is 2.22 ~ 2.65 g/cm3, and the internal structure is dense and hard, so the specific gravity is also very large, which is one of the methods to distinguish the authenticity of crystal. Rock crystal will feel obviously heavy in his hand, while the fake crystal will obviously feel very light.
In jewelry science, Mohs hardness in mineralogy is used to indicate the hardness of jewelry and jade. The Mohs hardness test method is a qualitative grade determined according to the relative hardness of 10 standard minerals, and Mohs hardness is divided into 10 grade. The higher the hardness grade, the better the durability of jewelry and jade.
According to the test, the hardness of crystal is 7, which belongs to the upper-middle level in jewelry and jade. For example, the hardness of glass is 5, and the hardness of glass is lower than that of crystal. Therefore, if you scratch the crystal surface with glass, there will be no scratches on the crystal surface. On the contrary, if you scrape the glass surface with crystal, there will be scratches on the glass surface.
According to the color and special optical effects, crystals can be divided into different gem varieties:
(1) Colorless crystal: colorless and transparent, with pure composition and transparency, it is difficult to see large crystals without inclusions and cracks. One is used as a carving material, and the most famous one is to make crystal balls, which are mainly used as family decorations. The world's largest flawless crystal sphere, with a diameter of 2 1cm, is now in the Smithsonian Museum in Washington, USA.
(2) Amethyst: Generally, the color is light and the color distribution is uneven. Amethyst also includes purple and crimson transparent water crystals. It is the most expensive crystal, the birthstone of February, and often has obvious dichroism.
(3) Topaz: Because it contains a small amount of Fe, it is yellow-orange-red and brown-yellow, mostly transparent columnar crystals. At present, the yellow-brown crystal of amethyst can often be seen in the market.
(4) Smoke crystal, tea crystal and ink crystal: smoke yellow crystal, dark brown crystal and black crystal. Some people think that these crystals are mainly caused by uniformly distributed carbon mixed with different amounts of ultrafine particles, others think that these crystals are formed because they contain tiny particles (such as a large number of gases or free silicon atoms), and still others think that the crystals contain a small amount of A 1 and A 13+ ions instead of Si.
(5) Hair crystal: a crystal variety containing slender rutile hair, black or colored tourmaline, green amphibole, white asbestos, actinolite as bright as silk, etc. This inclusion makes the crystal very beautiful. This crystal can be used as an ornament without fine processing.