The chemical composition of coral is mainly CACO3, which is generally translucent or opaque and can be white, red, black and so on. It is the skeleton of coral, so it preserves some structural characteristics of coral growth. For example, along the longitudinal direction of coral branches, they are always banded or striped. But the cross section of coral branches is concentric circles. Pink and white corals as gems have a specific gravity of 2. 6 - 2。 7, the refractive index change is 1. 48 - 1。 About 66. It bubbles when it comes to hydrochloric acid.

Coral-like materials in the market mainly include dyed marble, pink glass and plastic, Lulu and gilson synthetic coral products.

The difference between coral-like substances and corals can be based on the unique striped structure of corals. If there is HCL, it is easier to identify, because corals will foam when they meet HCL; On the other hand, it must be an imitation (of course, the use of this method is limited to a large number of tests because it is a destructive method).

The difference between natural coral and synthetic coral in gilson is that the synthetic product is fine-grained structure, not striped structure; In addition, the surface of natural coral often has some small and shallow circular pits, which are the growth parts of coral and also the identification signs.

Coral can also be dyed, such as stone or white coral dyed red, just like red coral. In this case, it can be tested by gently wiping with a cotton swab dipped in acetone. If it is dyed, the red will stay on the cotton swab.

At present, there is no recognized system for the price of coral, which is generally divided into three grades according to the source of coral. One is live coral, which has a compact structure and good luster and is the best raw material. The second kind is an inverted coral, that is, a coral that has stopped growing but has not been eroded by seawater. Third, dead corals, that is, the skeletal remains of corals after death, generally have holes and loose structures. Coral products can generally be classified according to color. Crimson coral is the most precious, followed by pink, and white and black are worse. In addition to color, whether the luster of coral is bright after polishing and particle size are also an evaluation factor. The price of large particles, strong luster and compact structure is higher. The price of different quality varies greatly, ranging from tens of yuan to several thousand yuan.

About the maintenance of coral. As long as it is not in contact with acid and alkali, it can be washed with water after each wear.