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Precious Coral Gemstones

Natural Red Coral
Natural Red Coral

There is a small but important class of gemstones that are not really stones at all. Rather than being minerals with a crystalline structure, their origin is organic - they formed from biological processes, whether animal or vegetable. The class of organic gems is small but includes a number of unusual varieties that are important in the gem trade; amber, coral, jet, ivory and pearl.

Coral is a branching skeleton-like structure built by small marine animals known as coral polyps. Gem-quality coral is related to reef-forming coral, but the most valuable coral variety is found in the Mediterranean, the Red Sea and in coastal Japan. Colors vary and can be bright-red to dark-red, orange-red, orange-pink, pink, white, blue or black. Unworked coral is dull, but when polished, coral exhibits an attractive vitreous luster.

Precious Coral Cabochons
Precious Coral Cabochons

Precious coral is a species of coral that grows on rocky sea beds, typically in dark environments, either in the depths of the ocean or in dark caverns. The coral skeleton is composed of hard calcium carbonate colored by carotenoid pigments. Coral typically exhibits a range of warm reddish-pink colors ranging from salmon-pink to deep-red. The word 'coral' is also used to refer to such colors. However, gem-quality coral is also found in white, black and blue.

Red Coral Cabochon
Red Coral Cab

Due to its intense coloration and luster, precious coral has been harvested since antiquity for decorative use. Coral jewelry has been found in ancient Egyptian and prehistoric European burials. Most precious coral is harvested in the Mediterranean Sea, especially in Sardinia. Deposits are also found in the Pacific, in Japan, Taiwan and Australia.

Since coral is an organic material, it is not especially durable. Coral is reasonably hard, but not nearly as hard as many gemstones; it has a rating of only 3 to 4 on the Mohs scale. Coral is sensitive to heat, acid and high temperatures, and the color can fade slightly with wear. White and red coral has a specific gravity or density of 2.60 to 2.70 and a refractive index of 1.486 to 1.658. Coral is translucent to opaque.

Coral is polished with fine-grained sandstone and emery, and then finely polished with felt-wheels. It is used for beads, cabochons, ornamental objects and sculptures. You will sometimes see branch-like pieces that are drilled and strung on spiky necklaces.

  • Première publication: 02 Juillet 2008
  • Dernière mise à jour: 23 Janvier 2019
  • © 2005-2021 GemSelect.com tous droits réservés.
    Reproduction (texte ou graphique), sans le consentement écrit de GemSelect.com (SETT Company Ltd) est strictement interdite.
Plus de formes
Pierres précieuses populaires
  • Saphir
  • Émeraude
  • Rubis
  • Aigue marine
  • Zircon
  • Opale
  • Topaze
  • Tourmaline
  • Grenat
  • Améthyste
  • Citrine
  • Tanzanite
Toutes les pierres précieuses (140)
A B C D E F G H I J K L M N O P Q R S T V Z
  • Actinolite Œil de chat
  • Agate
  • Agate Géode
  • Agate de Feu
  • Aigue marine
  • Amazonite
  • Ammolite
  • Améthyste
  • Amétrine
  • Andalousite
  • Andésine Labradorite
  • Apatite
  • Aventurine
  • Béryl
  • Béryl doré
  • Calcédoine
  • Charoïte
  • Chrysobéryl
  • Chrysocolle
  • Chrysoprase
  • Citrine
  • Clinohumite
  • Corail
  • Corail de Fossile
  • Cornaline
  • Dendritique Agate
  • Diamant
  • Diaspore Couleur Changeant
  • Diopside Chrome
  • Diopside Étoilé
  • Disthène
  • Druse d'améthyste
  • Druzy Azurite
  • Enstatite
  • Flocon de Neige Obsidienne
  • Fluorine
  • Fluorite avec changement de couleur
  • Grandidierite
  • Grenat
  • Grenat Almandin
  • Grenat Couleur Changeant
  • Grenat Démantoïde
  • Grenat Grossulaire
  • Grenat Hessonite
  • Grenat Malaya
  • Grenat Mali
  • Grenat Pyrope
  • Grenat Rhodolite
  • Grenat Spessartite
  • Grenat Tsavorite
  • Grenat Étoilé
  • Howlite
  • Hématite
  • Hémimorphite Druse
  • Idocrase
  • Iolite
  • Jadéite
  • Jaspe
  • Jaspe Sanguin
  • Kornerupine
  • Kunzite
  • Labradorite
  • Lapis-lazuli
  • Larimar
  • Malachite
  • Maw-Sit-Sit
  • Morganite
  • Nacre
  • Nuummite
  • Obsidienne
  • Oeil de Chat Aigue-Marine
  • Oeil de Chat Quartz
  • Oeil de Tigre
  • Oeil de Tigre Matrice
  • Oeil de chat Apatite
  • Oeil de chat Scapolite
  • Oeil de chat Sillimanite
  • Oeil de chat de la Pierre de Lune
  • Onyx
  • Opale
  • Opale Boulder
  • Opale Chocolat
  • Opale Doublet
  • Opale Noir
  • Opale de Feu
  • Opale en Matrice
  • Opale hyalite
  • Opale œil de chat
  • Perle
  • Pierre de Lune
  • Pierre de Lune Arc en Ciel
  • Pierre de Lune Étoilé
  • Pierre de Soleil Étoilé
  • Pierre de Soleil 
  • Pierre précieuse étoiles
  • Pierres précieuses Jade
  • Pierres précieuses de couleur changeante
  • Pierres précieuses oeil de chat
  • Pietersite
  • Prehnite
  • Pyrite
  • Pyrite Arc en Ciel
  • Péridot
  • Quartz
  • Quartz Citron étoilé
  • Quartz Fraise
  • Quartz Rose
  • Quartz Rose Étoilé
  • Quartz Rutile
  • Quartz avec marcassite
  • Rhodochrosite
  • Rubellite Tourmaline
  • Rubis
  • Rubis en Fuchsite
  • Rubis Étoilé
  • Rubis-Zoisite
  • Saphir
  • Saphir couleur-Changeant
  • Saphir Étoilé
  • Scapolite
  • Scolécite
  • Seraphinite
  • Serpentine
  • Sillimanite
  • Smithsonite
  • Sodalite
  • Spectrolite
  • Sphalérite 
  • Sphène
  • Spinelle
  • Tanzanite
  • Topaze
  • Topaze Imperiale
  • Topaze Mystique
  • Tourmaline
  • Turquoise
  • Variscite
  • Zircon
  • Émeraude
  • Œil de faucon
Catégories principales
  • Nouveautés
  • Lots de pierres précieuses
  • Pierres précieuses calibrées
  • Pierres gemmes à la pièce
  • Des pierres précieuses d'excellentes qualités
  • Paires correspondant
  • Pierres précieuses cabochon
  • Gemmes, briolettes et perles percées
  • Pierre de naissance
  • Sculptures en pierres précieuses
  • Pierres précieuses fantaisie
  • Pierre précieuse étoiles
  • Saphir non chauffé
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Taille et poids

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

Size Comparison Chart