Precious coral, a gift from the ocean / Japan Coral Association
Octocorallia and hexacorallia / Growth / Coraland people /
How to harvest / Where to harvest / Conservation

Octocorallia and hexacorallia

Octocorallia (precious coral)
Most live at a depth of 100 meters (328 feet) in the sea off Japan.
Some even live at a depth of more than 1,000 meters (3,280 feet).

Hexacorallia (reef-building coral)
Most live at a depth of approximately 30 meters (98 feet).

Octocorallia (precious coral)

This is a group of hard coral species living at a depth of more than 100 meters (328 feet) where no sunlight reaches. Precious coral is a member of this group. This is a very slow growing species, formed by polyps with eight tentacles which capture floating materials of up to several hundred microns. (One micron is one millionth of a meter or approximately 1/25000 of an inch.) This coral is as hard as human teeth and equal to a hardness of 3 on the Mohs scale. Precious coral jewelry has attracted people worldwide since ancient times because of its beautiful luster when polished.

Hexacorallia (reef-building coral)

This is a group of several hundred reef-building coral species including familiar names such as table coral, cup coral, and stony coral, and sea anemones. The polyps of this coral have tentacles in groups of six, instead of eight. Symbiotic algae called zooxanthellae live in the tissues of this coral, carrying out photosynthesis. This activity reflects that these species live in shallow (less than 50 meters or 165 feet) and warm (above 20 degrees Celsius or 68 degrees Fahrenheit) coastal waters in the tropics and subtropics. This coral is home to a diversity of marine species though is not suitable for jewelry because it is spongy and porous.

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