Coral

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Coral has been prized throughout history for its natural beauty. Like pearl, coral is also an organic gem consisting of more than 90% calcium carbonate. All coral consists of the remains of skeleton-like support structures that were built by colonies of very small marine animals, known as coral polyps. Proteinaceous coral differs from calcareous coral because it is made up of strong keratin proteins.

Coral Rough
Coral Classification
Common Name Coral
Species Organic
Coral Optical Properties
Transparency Semitranslucent - Opaque
Refractive Index 1.560-1.570
Tolerance:(+0.010/-0.010)
Polariscope Reaction Aggregate (AGG)
Fluorescence SWUV: White:inert to weak to strong bluish whiteLight and dark orange, red and pink: inert to orange to pinkish orangeDark red: inert to dull red to purplish red
LWUV: White:inert to weak to strong bluish whiteLight and dark orange, red and pink: inert to orange to pinkish orangeDark red: inert to dull red to purplish red
Pleochroism None
Coral Characteristic Physical Properties
Hardness 3
Specific Gravity 1.300-2.120 Typical:1.350
Toughness Fair
Inclusions Calcareous coral has a wavy fibrous structure with polyp cavities in cross section the branches have concentric web like structure.
Luster Vitreous, Waxy
Fracture Uneven, Splintery
Cleavage None
Coral Chemistry & Crystallography
Chemical Formula C32H48N2O11
Crystal System NA
Chemistry Classification Organic

Alternate Names

Black Coral, Golden Coral, King's Coral, Akori Coral

Countries of Origin

Afghanistan; United States of America (the); Malaysia; Thailand; Taiwan (Province of China); India; Pakistan; Morocco; China; Italy; Mexico; Australia; Indonesia

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Simulants

Gilson Imitation Coral

A synthetic, imitation coral made from calcite and silica, Gilson imitation coral requires heat and pressure to create the final product.This imitation does not exhibit the natural grains often visible in true coral, and shows fine granulation under magnification.

Gilson Imitation Coral Coral
Gilson Imitation Coral Classification
Common Name Gilson Imitation Coral
Gilson Imitation Coral Optical Properties
Refractive Index 1.55
Fluorescence LWUV: Variable
Gilson Imitation Coral Characteristic Physical properties
Inclusions Natural coral will have polyp cavities and fibrous structure imitation coral will have a granular structure under magnification.

Species/Variety

Coral (Calcareous)

Coral has been prized throughout history for its natural beauty. Like pearl, coral is also an organic gem consisting of more than 90% calcium carbonate. All coral consists of the remains of skeleton-like support structures that were built by colonies of very small marine animals, known as coral polyps. Proteinaceous coral differs from calcareous coral because it is made up of strong keratin proteins.

Coral (Calcareous) Coral
Coral (Calcareous) Classification
Common Name Coral (Calcareous)
Coral (Calcareous) Optical Properties
Refractive Index 1.486-1.658
Birefringence 0.172
Coral (Calcareous) Characteristic Physical properties
Specific Gravity 2.6
Inclusions Calcareous coral has a wavy fibrous structure with polyp cavities in cross section the branches have concentric web like structure.

Coral (Proteinaceous)

Coral has been prized throughout history for its natural beauty. Like pearl, coral is also an organic gem consisting of more than 90% calcium carbonate. All coral consists of the remains of skeleton-like support structures that were built by colonies of very small marine animals, known as coral polyps.

Coral (Proteinaceous) Coral
Coral (Proteinaceous) Classification
Common Name Coral (Proteinaceous)
Coral (Proteinaceous) Characteristic Physical properties
Inclusions In cross section conchiolin coral has a tree ring like growth structure with concentric and circular rings. Sometimes the rings will look like white crescents.The surface of the branch will have a bumpy appearance.Black coral is sometimes bleached to look like golden coral and will visually appear to have a rougher texture.
Tim Matthews

Author

Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.