The crystal is colorless and transparent, and its main chemical component is silicon dioxide. When the silicon dioxide crystal is perfect, it is a crystal; When the particle size of silica is less than several microns, chalcedony, flint and secondary quartzite are formed. Crystals include white crystal, amethyst, topaz, tea crystal, pink crystal, ivory crystal and so on.

True and false identification:

1. The difference from synthetic crystal: synthetic crystal is more expensive than ordinary rock crystal: there is no need to identify the authenticity. However, if the crystal ball and amethyst with a diameter greater than 10 cm are much more expensive than the synthesizer, it is necessary to correctly identify them. Natural amethyst has uneven color distribution and often contains inclusions, while synthetic amethyst has uniform color and pure interior.

2. Difference from glass: Because the hardness of glass is lower than that of crystal, crystal can always carve glass, but glass can't carve crystal. Because of the high thermal conductivity of crystal, it feels cold to the touch, but glass is not.

Quality evaluation: the most popular crystal is purple; It has starlight and cat's eye effect, good effect and high value; Some inclusions and crystals with special shapes, such as mountains, water, flowers, birds, figures and characters, are very rare ornamental stones.