History & Introduction

The coral gemstone is a quality variety of natural coral and is closely related to reef-building 'stony' coral. The coral stone that is valuable is a deep water coral that is formed in rocky sea beds, which possess low levels of sedimentation, naturally in dark environments of over 500 feet deep adding up to caverns and crevices. Coral is gradually built by very small marine animals called coral polyps. Such small soft-bodied creatures created by with minute, hard shells that accumulate as the colony grows. With time, the colony is formed to complex branches and skeletal structures composed with hardened calcium carbonate, and coloured by carotenoid pigments.

Maximum coral gemstones available currently, are varieties of Corallium rubrum, a very specific pink to red colour species of the coral genus. In the trade, there are times when Corallium rubrum is referred as 'noble coral' and is considered to be the coral highest in demand jewelry. Noble coral even includes the famous 'angel skin coral', a pink to salmon colour coral. Corallium rubrum, along with fossil coral, coral sand, agatized coral and coral fragments are not regulated or protected from international trade that means it is possible to import and export to maximum countries without permits.

There are more than 2,500 varieties of corals in nature that are distinguished as the palette of 350 colours. Originally, they are dim, however they receive strong glass glitter that is polished; coloration it is both uniform and patchy. When polyps and "fleshy" skin is removed, a coral is used like pearls and goes for the manufacture of various interior decorations and jewellery.

In Europe corals are a symbol of modesty. As per legends and beliefs, they guard from witchcraft and poisons, are advantageous against breathlessness, forgetfulness, loss of appetite, nervous tic, and nerve attacks. Corals provide strength to heart and reduce heart palpitations, it cures sadness. These semi-precious stones are also used to treat eyes. Ancient Greeks considered the pink coral as a symbol of immortality and happiness.

During middle period it was said that corals formed a man wise, prevented trouble, healed wounds and lowered fever and even to be successful in relations with the opposite sex. It is even believed that by burning and sprinkling on the old ulcers, then you can dry them, remove cancerous growths: corals heal and purify them so that there will be no trace. It helps to avoid hatred, envy and anger; for that it needs to be worn as a ring on the middle finger of the right hand. Ancient Romans thought that burned, pounded and dropped in water corals gives relief to people who are suffering from spasmodic pain intestine, in diseases of the stomach, bladder and spleen.

Coral, was classed with precious gems and was found adorning ancient amulets with emerald, pearl, diamond and ruby, and also it was proved experimentally by the sixteenth century to cure madness, provide wisdom, to cure the flow of blood from a wound. It was also popular to prevent sterility.

Coral lost its popularity for a while, however it again steadily start gaining popularity in these years. This material is from semi-translucent to opaque material created a colony of marine invertebrates, is mainly a skeletal calcium carbonate gem. The formation as seen in the water look like tree branches. Coral gemstone is available in a wide range of colours. It is one of the most expensive varieties and has becomes very popular in recent years and is used widely for jewellery purposes. At present, the rarest and the most expensive variety found is blood coral, even famous as noble or oxblood coral. This variety is very deep red.

It is a very a soft stone, so some precautions are taken when wearing it. Due to its calcium composition, you must be careful to avoid contact with acid like the vinegar in a salad that you might toss your hands.

Recognise - Coral is an organic material and it is a soft stone so it not a durable gemstone. It has hardness from 3 to 4 on the Mohs scale that is easily helpful to discern and identify coral from alike gemstones like carnelian, rhodonite or spessartite garnet. Red and white coral with a composition of calcium carbonate has a specific gravity or density from 2.60 to 2.70 and even the refractive index from 1.486 to 1.658. These specific gemmological properties, combined with coral's translucent to opaque form, it easy to recognize natural coral gemstone from imitations or similar gemmy materials.

Availability - Although we get precious coral gemstone from locations all around the world, Torre del Greco (near Naples, Italy) is said to be the top coral trading centre for over 200 years, processing nearly 75% of the entire world's supply of coral. Maximum valuable coral available today is harvested from the western Mediterranean Sea, particularly in Sardinia. Notable deposits are also found in the Red Sea, the Malaysian Archipelago, the Taiwan, the Bay of Biscay, Midway Islands, Japan, Australia and the Hawaiian Islands. The valuable coral found in Hawaii, coastal Japan, the Mediterranean and the Red Sea is considered to be the finest coral at present.

Usages - Coral gemstone is used as beads and cabochons. It is even sculpted into small carvings like flowers for pins and brooches. At times the tiny branches of Coral are stranded into spiky, dangling necklaces. Hawaiian golden coral, black ("akkabar", or "royal coral") coral, blue ("acorea") coral, red and pink precious corals are particularly treasured in a jewellery production. Corals have been a favourite decoration since ancient times. Maximum the red varieties are in used.

Buying Guide

Colour - The valuable coral stone naturally shows a range of warm pinkish to red colours that includes light-red to salmon (momo coral) with medium-red (Sardegna coral) to deep ox-blood red (moro coral); colour is said to get fade after it is worn. Noble coral consist of the most desirable uniform colour, but it displays streaks or spots of white to pinkish red, particularly angel skin coral. This gemstone is also found in other colours like blue, gold, black and white. Gold colour coral from Hawaii is tremendously rare and highly in demand due to its slight chatoyancy. Blue and black coral gemstone is not often used for gems or jewellery as its trade is heavily regulated.

Clarity and Lustre - Naturally the stone is translucent to opaque. After it is unworked, it consist of naturally dull, matte lustre. Polished coral shows an attractive vitreous lustre. Coral stone is polished with emery as well as fine-grain sandstone, and then with felt-wheels it is finely polished.

Cut and Shape - Due to its softness and opacity precious coral is mainly cut en cabochon. It is generally used for sculptures, beads, ornamental and carvings. Cabochons is found in just about any shape, however the most post shapes it is found are ovals, rounds and free-form shapes.

Treatment - Natural coral is not treated, however there are materials that are dyed to get a more valuable colour. There are a variety of other materials used to imitate coral, like glass, bone, plastic and conche pearl.

Gemological Characteristics:

Chemical Formula	CaCO3, Calcium carbonate - organic
Crystal Structure	(Trigonal) microcrystalline
Colour	Red, black, white, blue, pink
Hardness	From 3 to 4
Refractive Index	White and red: from 1.486 to 1.658
Density	White and red: from 2.60 to 2.70
Cleavage	Not available
Transparency	From translucent to opaque
Double Refraction or Birefringence	White and red: -0.160 to -0.0172
Lustre	Unworked dull, polished vitreous
Fluorescence	Weak; violet
SG	From 2.6 to 2.7

Classification:

• Black Coral
• Precious Coral
• Red Coral