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: Coral Gem Info

Coral Gemstone Information

About Precious Coral - History and Introduction

Precious coral is a gemstone quality variety of natural coral, closely related to reef-building 'stony' coral. Precious coral is a deep water coral that forms in rocky seabeds with low levels of sedimentation, typically in dark environments of over 500 feet deep, including caverns and crevices. Precious coral is slowly built by very small marine animals known as coral polyps. These tiny, soft-bodied creatures form with minute, hard shells that accumulate as the colony grows. Over time, the colony begins to form complex branches and skeletal structures composed of hardened calcium carbonate, and colored by carotenoid pigments. These biological formations grow very slowly, often as little as just 1 millimeter per year, ranging in size from small, hand-sized structures to enormous coral reefs.

Most coral gemstones available today are varieties of Corallium rubrum, a very specific pink to red colored species of the coral genus. In the trade, Corallium rubrum is sometimes referred to as 'noble coral' and is considered to be the most desirable type of coral for jewelry. Noble coral also includes the popular 'angel skin coral', a pink to salmon colored coral. Corallium rubrum, along with fossil coral, agatized coral, coral sand and coral fragments are not regulated or protected from international trade, meaning that they can be imported and exported to most countries without permits. However, coral of Hawaiian origin is protected under the Lacey Act and cannot be harvested and exported from the USA. Other types of regulated coral (mostly from China and Hawaii) include Corallium japonicum, Corallium elatius, Corallium secundum and Antipathes grandis. Although these may require permits for international trade, they can usually be traded domestically.

Carved Coral Cabochon
Natural Precious Coral
Click to enlarge image
Identifying Coral Back to Top

Coral is an organic material and like other organic gemstones, it is not an especially hard or durable gemstone. It has a hardness rating of 3 to 4 on the Mohs scale, which can easily help distinguish and identify coral from similar colored gemstones such as carnelian, rhodonite or spessartite garnet. White and red coral with a calcium carbonate composition has a specific gravity or density of 2.60-2.70 and a refractive index of 1.486-1.658. These specific gemological properties, combined with coral's translucent to opaque form, can easily help identify natural coral from imitations or similar gemmy materials.

Coral Origin and Gemstone Sources Back to Top

Though precious coral is found in locations all around the world, Torre del Greco (near Naples, Italy) has been the top coral trading center for over 200 years, processing nearly 75% of the entire world's supply of coral. Most of the precious coral available today is harvested from the Western Mediterranean Sea, especially in Sardinia. Notable deposits are also found in the Red Sea, the Bay of Biscay, the Malaysian Archipelago, the Midway Islands, Japan, Taiwan, Australia and the Hawaiian Islands. Precious coral from Hawaii, coastal Japan, the Mediterranean and the Red Sea is considered to be the finest coral of today.

Buying Coral and Determining Coral Gemstone Value Back to Top

Coral Color

Precious coral typically exhibits a range of warm pinkish to red colors, including light-red to salmon (momo coral), and medium-red (Sardegna coral) to deep ox-blood red (moro coral); color is known to fade when worn. Noble coral has the most desirable uniform color, but can often exhibit streaks or spots of white to pinkish red, especially angel skin coral. Precious coral can also be found in other colors such as gold, white, black and blue. Gold colored coral from Hawaii is extremely rare and highly desired for its slight chatoyancy. Black and blue coral is not often used for gems or jewelry as its trade is heavily regulated.

Coral Clarity and Luster

Precious coral is typically translucent to opaque. When unworked, it has a naturally dull, matte luster. Polished coral exhibits an attractive vitreous luster. Coral is polished with fine-grain sandstone and emery, and then finely polished with felt-wheels.

Coral Cut and Shape

Precious coral is most often cut en cabochon due to its softness and opacity. It is popularly used for beads, ornamental carvings and sculptures. Cabochons can be found in just about any shape, but ovals, rounds and free-form shapes are most popular.

Coral Treatment

Natural coral is typically untreated, but some materials may be dyed to achieve a more valuable color. There are a variety of other materials used to imitate coral, such as glass, bone, conch shell and plastic.

Coral Gemological Properties: Back to Top
Chemical Formula: CaCO3, Calcium carbonate - organic
Crystal Structure: (Trigonal) microcrystalline
Color: Red, pink, white, black, blue
Hardness: 3 to 4 on the Mohs scale
Refractive Index: White and red: 1.486 to 1.658
Density: White and red: 2.60 to 2.70
Cleavage: None
Transparency: Translucent to opaque
Double Refraction or Birefringence: White and red: -0.160 to -0.0172
Luster: Unworked dull, polished vitreous
Fluorescence: Weak; violet

Please refer to our Gemstone Glossary for details of gemology-related terms.

Coral: Gemstone Varieties or Similar Gemstones: Back to Top
Fossil Coral
Fossil Coral

Precious coral belongs to a small, but important group of gemstones, which technically are not stones at all. Rather than being minerals with crystalline structures like most colored stones, coral is formed through a biological process and thus belongs to an elite class of organic gems. Although the class of organic gemstones is rather small, there are a number of very unusual and important gemstone varieties within the group. There are a few materials that can be mistaken for coral owing to similarities in color or texture, including conch pearl, carnelian (red agate), rhodonite, spessartite garnet, glass, horn, rubber (gutta-percha), bone and plastic.

Most Popular Similar or Related Materials:

Amber, ammolite, jet, ivory and pearl are the most popular and well-known related gemstones.

Lesser-Known Similar or Related Materials:

Fossil coral and agatized coral are rarer and lesser-known related gemstones.

Coral Gemstone Mythology, Metaphysical and Alternative Crystal Healing Powers Back to Top

Since the beginning of the 1st millennium, precious coral has been highly prized as a gem believed to be endowed with mysterious, powerful and sacred properties. The Gauls often used coral gems as ornamentation for their helmets and weapons in the belief that it was a protective stone. Ancient Egyptians also placed coral in tombs of the deceased to protect against evil spirits because they believed each coral gem actually contained divine blood. The Romans hung branches of coral around the necks of their children to protect them from danger. In the early 20th century, the people of Italy used coral for protection from the 'evil eye' and many Italians used it for infertility.

In the Jyotish and Vedic practice of planetary gemology, red coral is the planetary stone for Mars. The Pueblo Indians considered coral to be one of the four elemental stones. Among the Hopi and Zuni tribes, the 'road of life' is symbolized by coral, jet, abalone and turquoise (the four elements). Although precious coral is not a traditional birthstone for any month, it is a zodiac stone for Pisces, Scorpio, Capricorn and Taurus. Red coral is ideal for the root or base chakra and pink coral can be beneficial for the heart chakra.

Disclaimer: Metaphysical and Alternative Crystal Healing Powers and Properties are not to be taken as confirmed advice. Traditional, Ceremonial and Mythological Gemstone Lore is collected from various resources and is not the sole opinion of SETT Co., Ltd. This information is not to replace the advice of your doctor. Should you have any medical conditions, please see a licensed medical practitioner. GemSelect does not guarantee any claims or statements of healing or astrological birthstone powers and cannot be held liable under any circumstances.
Coral Gemstone and Jewelry Design Ideas Back to Top

Due to its intense and permanent coloration and attractive luster, precious coral has been harvested since antiquity for decorative and ornamental jewelry use. Precious coral is often used for beads in string jewelry such as necklaces and bracelets. You will sometimes see branch-like pieces drilled and strung as spiky necklaces. Cabochons and carvings of flowers or other ornamental objects are quite often used for the making of pendants, pins and brooches. Coral is not recommended for everyday rings, but if set in protective-style settings they can be worn in occasional-wear rings with care.

Note: Buy colored gemstones by size and not by carat weight. Colored stones vary in size-to-weight ratio. Some stones are larger and others are smaller than diamond by weight in comparison.

Coral Gemstone and Jewelry Care and Cleaning Back to Top

How to clean your gemstonesPrecious coral is not very durable compared to most of the other gemstones used today for jewelry and therefore requires a bit more care and maintenance than most other jewelry gemstones. Coral is very sensitive to acid and heat. Color is also known to fade with wear and tear. To reduce color loss, avoid exposing your gem to direct sunlight for prolonged periods of time and avoid any extreme temperature fluctuations. Do not clean your coral with any harsh household cleaners, such as bleach or acid, and avoid spraying perfumes or hairspray while wearing your coral gems or jewelry.

You can wipe down precious coral using a soft cloth and a mild soap or detergent if needed. Be sure to rinse well using warm to room-temperature water to remove soapy residue. Because precious coral is much softer than quartz, simply wiping dust off can eventually lead to reduced polish. To prevent scratches avoid wearing other gems in close contact with your coral jewelry. Always remove jewelry before exercising, playing sports or performing any household chores. When storing your coral gemstones, wrap them individually using a soft cloth and store them away from other gems. If possible, place them inside a fabric-lined jewelry box for extra protection.

  • First Published: November-29-2013
  • Last Updated: October-12-2017
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    Reproduction (text or graphics) without the express written consent of GemSelect.com (SETT Company Ltd.) is strictly prohibited.
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Size and Weight

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

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