About coral species, living environment, and can be made into coral crafts and so on.

Corals are a kind of marine cylindrical coelenterates called "coral polyps" among the living organisms. In the white larval stage, it automatically fixes itself on the limestone remains of its predecessor coral. The chemical composition of coral is mainly CaCO3, which exists in the form of microcrystalline calcite aggregates, and there is also a certain amount of organic matter in the composition. The morphology is mostly dendritic with longitudinal stripes. Each single coral cross-section has concentric circles and radial stripes. The color is often white, but also a small amount of blue and black. Gem grade corals are red, pink, and orange-red. The red color is formed due to coral absorbing about 1% of iron oxide in seawater during growth, and the black color is due to the presence of organic matter. With glassy to waxy luster, opaque to translucent, refractive index 1.48-1.66. hardness 3.5-4, density 2.6-2.7g/cm3, black coral density is lower, for 1.34g/cm3. brittle. Brittle, strong blistering in hydrochloric acid. No fluorescence.

The image of coral is like a tree branch, the color is bright and beautiful, can be used as decorations.

The ancient Romans believed that coral has the function of preventing disasters, giving people wisdom, stopping bleeding and driving away heat. It has a close relationship with Buddhism, India and China Tibetan Buddhists regard the red coral is the embodiment of Buddha, they put the coral as a sacrifice to the Buddha's good luck, more used to do Buddha beads, or used to decorate the statue of God, is a highly prized jewelry gemstone varieties. Stony coral (stony coral order [Madreporaria or Scleractinia]) about 1,000 species; black coral and spiny coral (horn coral order [Antipatharia]) about 100 species; willow coral (or horn coral, willow coral order [Gorgonacea]) about 1,200 species; and blue coral (blue coral order [Coenothecalia]) about 1,200 species; blue coral (blue coral order [Coenothecalia]) about 1,200 species. Coenothecalia) is the only surviving species. Soft corals, willow corals and blue corals live in groups. Each hydroid in the colony has eight tentacles, and there are eight septa in the gastric circulation cavity, six of which have cilia to direct water into the gastric circulation cavity, and two of which have cilia to direct water out of the gastric circulation cavity. The skeleton is an endoskeleton. Soft corals are widespread and their skeletons consist of calcium-containing bone needles separated from each other. Some species are disk-shaped, others have finger-like projections (e.g., species of the genus Alcyonium, commonly known as dead man's fingers). Horn corals are abundant in shallow tropical seas and are banded or branched in shape, reaching lengths of up to 3 meters (10 feet). Horn coral including the so-called noble coral (also known as red coral, rose coral), can be used as jewelry, of which the common species are the Mediterranean red coral (Corallium rubrum). Blue coral (Heliopora coerula, deep green pale coral) in the Indian and Pacific Oceans in the formation of stony coral on the reef, the formation of up to 2 meters in diameter block.

Stony corals are the best known and most widely distributed species, living singly or in groups. As with black coral and stinging coral, the septa are 6 or multiples of 6, and the tentacles are simple and not pinnate. Stony, black, and stinging corals differ from related anemones mainly in having exoskeletons. Stony corals are found in all oceans, from the tidal zone to depths of 6,000 meters (about 20,000 feet). Species that live in colonies have hydrozoans 1?6?530 mm (0.04?6?51.2 in) in diameter. Most living stony corals are light yellow, light brown, or olive colored, depending on the algae living on the coral. However, their skeletons are always white. The largest single-living stony coral is a Fungia, which can be about 25 centimeters (10 inches) in diameter.

The skeleton of a stony coral is cup-shaped, encasing the body of a hydroid, and is composed almost entirely of calcium carbonate. Its growth rate depends on age, food supply, water temperature, and species. Atolls and reefs are formed from the skeletons of stony corals, and their rate of formation averages about 0.5?6?52.8 centimeters per year. Common stony coral species include nauk coral, mushroom coral, star coral, and staghorn coral, all named after their morphology.

Black and spiny corals are whip-like, feathery, tree-like or shaped like a bottle brush, and are found in the Mediterranean Sea, the West Indies, and the coastal waters of Panama.

An airborne ingredient that makes corals susceptible to death has been found in some coral areas due to environmental pollution, and as a result, coral species and populations have declined dramatically around the world.

Red coral growth environment Grows in the temperature higher than 20 ℃ equator and nearby tropical, subtropical areas, water depth of 100-200 meters of calm and clear reefs, platforms, slopes and cliff faces, crevices. Mainly produced in the Mediterranean Sea. According to the ecological environment and characteristics of stony coral growth, and can be divided into reef-building stone coral; non-reef-building stone coral (or deep-water stone coral) 2 categories.

Stone coral in the deep water stony coral, as the name suggests they inhabit the deep sea. Known to inhabit the deepest record is found in the Aleutian trench 6296 ~ 6328m in the Aleutian symmetric bacteria cup coral (Fungiacyathus symmetricus aleuticus). Deep-water stony corals are generally dominated by singles, a few groups, and small individuals with monotonous coloration. They can be harvested with trawls and mud harvesters at different depths in the ocean.

Shallow water stony coral distribution in shallow water, generally from the water surface to the water depth of 40m, individual species distribution can be as deep as 60m. the vast majority of groups. In the tropical sea area growth flourish. They live in the water colorful, colorful, the tropical seaside dotted with extra dazzling, so the shallow water coral area has the beauty of the underwater garden.

In the tropical or subtropical zone of the India-Pacific waters and the Atlantic-Caribbean area have shallow water stony coral growth. However, due to geographic barriers (the Isthmus of Panama was formed 6 million years ago) the shallow-water stony corals of these two zones have evolved to form two distinct zones.

It has also been shown that the stony corals of the two zones are significantly different, both in number and species. It is known that there are 86 genera of stony corals in the Indo-Pacific region with more than 1,000 species (some say 500 or 800 species), while there are 26 genera and 68 species (or 25 genera and 50 species) in the Atlantic-Caribbean region.

Shallow water stony coral normal growth of seawater salinity of 27 ~ 42 ‰, and the requirements of clean water, but also need a hard substrate. In the estuary, due to the continental runoff into the sea, carrying a large number of land-based sedimentary material, thus not suitable for shallow stony coral growth. Therefore, it is futile to look for shallow stony corals in estuaries. The use of coral by humans dates back to ancient Greek and Roman times. Red coral from the Mediterranean Sea, then known in Japan as Kowatari ("Persian import"), was introduced to Japan via the Silk Road during the Nara period (710-784 AD). In medieval Europe, coral was used extensively in religious ceremonial ornaments and rosaries.

1Material composition: consists of two parts: inorganic and organic.

Inorganic: high magnesium calcite, a small amount of apatite, calcium carbonate, magnesium carbonate, a small amount of water, ferrous oxide, calcium hydroxyphosphate

Organic: mainly keratin.

2 structural features: waveform parallel fiber structure

along the longitudinal direction of the coral branches have color shades or different transparency to form a continuous waveform parallel fiber structure. The cross-section is concentric, like the annual rings of trees. There are many small round pits on the branches, which are the burrowing places of coral worms.

3Physical and chemical properties

Color deep red, fiery red mainly, and peach. Dendritic in shape. Skeleton dense and tough. Hm = 3.5-4, opaque - translucent. Raw material luster dark, polished wax-like luster, intolerant of acid, organic solvents and volatile gases.

Red coral culture in China, as well as India, Indian national traditional culture have a long history, especially the Indian indigenous peoples and Chinese Tibetans and other nomadic people on red coral is more favorite, and even the red coral as a body and pray for "heaven (emperor)" blessing of the trust object. According to the historical records, the utilization of red coral can be traced back to the ancient roman era. Ancient Romans believe that coral has to prevent disasters, give people wisdom, have stop bleeding and heat function, some seafarers believe that wearing red coral, can prevent lightning, hurricanes, so that the winds and waves, a safe journey! Therefore, the Romans called it "red gold", make red coral on a layer of mysterious color. Modern westerners coral and pearl and amber and listed as three major organic gemstones, is the western "March birthstone" one.