Coral can be divided into shallow water coral reef and deep-sea corals.
Shallow water coral reef has a wide distribution。There  has more isle form of coral reef in the area of shallow water of Pacific Ocean,Indian Ocean and Atlantic. The density of shallow water coral less than 2 ,and the rigidity of it less than 2 too.It can not be used to as the raw materials of the carving art, for viewing only as a Kistler.

Shallow water coral  also called “making reef coral”, by its development into a coral reef platform, can greatly ease the typhoons,storm surge and other natural disasters on the coast of ecological damage and therefore, the world environmental organizations to pass a resolution to ban logging shallow water coral stone, to protect the land Area will not be violated.

Deep-sea coral also known as the precious coral, is the general growth in the depth of 200 to 2000 meters of coral reef,the distribution of its has a limitations.For the process of petrifaction is completed in the deep sea, coral jade pore smaller, higher density (generally between 2.5 to 2.8), dense structure, changes in hardness between 3 to 4, it is the main raw materials of jewelry making,known as the precious coral.For the red coral is most precious in deep-sea coral,red coral has become a aynonym for the precious coral.

There are three main area of distribution  for deep-sea coral.
1, Taiwan area, southern Japan island(including the Ryukyu Archipelago);
2, The waters surrounding the Hawaiian Islands and Midway Island waters.
3, The Mediterranean coast,mainly for the south waters  of the Italian peninsula.

The formation of coral color.
Red corals grow on rocky seabottom with low sedimentation, typically in dark environments--either in the depths or in dark caverns or crevices. In fact, red coral in the distribution of deep-sea waters, seabed are of a large number of volcanic activity, these activities provide a lot of volcanic ash material, given ash material in a certain number of major elements (if any color element of iron,manganese, etc. and macroelement of magnesium, potassium, sodium, etc.) and trace elements (such as zinc, strontium, chromium, nickel,etc.).

Some girls all regard the coral necklace as the fashion necklace so they have  many different styles.Most of the modern coral necklaces are beaded jewelry.