Coral

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Australia
12.62 carats
© gemselect.com

The word Coral is derived from the ancient Greek word "korallion" - coral. Historically, this word was used to describe the precious red coral from the Mediterranean.

The Coral is a branching skeleton-like structure built by polyp-bearing marine animals that live in colonies and are found throughout the world in the seas and oceans from freezing polar regions to equatorial reefs and at all depths. The branches are generally 20-40 cm in hight and up to 6 cm thick.

Coral Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 
 

Coral Gemstones by Size

This table shows distribution of Coral gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.22 cts
Heaviest:61.71 cts
Average:18.86 cts
Total photos:43
Do you have a larger Coral? Why not upload a photo?
0.22ct to 6.37ct6.37ct to 12.52ct12.52ct to 18.67ct18.67ct to 24.82ct24.82ct to 30.97ct30.97ct to 37.11ct37.11ct to 43.26ct43.26ct to 49.41ct49.41ct to 55.56ct55.56ct to 61.71ct
General Information
Chemical Formula
CaCO
 
3
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Coral Treatments
Dyed: mostly with polymer treatment, color and resin concentration in fractures, cavities and branches junctions. Hot point test (acetone test in some cases) may reveal the treatment. Dyed pink to red from white variety: color dignostic if from "bamboo" type (natural color is white to brownish). Dyed blue from grayish: commonly with resin treatment: light blue color concentration in pits and cracks - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 9
Coral Simulants
Artificial pressed product (ceramics) consisting of calcite - Red; opaque; RI 1.486 - 1.658; Birefringence 0.172; Uniaxial/-; SG 2.60 - 2.70; Hardness 3.5 - 4; Trigonal. - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 3
Physical Properties of Coral
Mohs Hardness3 to 4
Walter Schumann, Gemstones of the world (2001)
More from other references
Specific Gravity2.60 to 2.70
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
TenacityBrittle
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityNone
Walter Schumann, Gemstones of the world (2001)
FractureIrregular,Splintery
Walter Schumann, Gemstones of the world (2001)
Optical Properties of Coral
Refractive Index1.486 to 1.658
Walter Schumann, Gemstones of the world (2001) White and redMore from other references
Optical CharacterUniaxial/-
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Birefringence0.160 to 0.172
Walter Schumann, Gemstones of the world (2001) White and redMore from other references
PleochroismAbsent
Walter Schumann, Gemstones of the world (2001)
DispersionNone
Walter Schumann, Gemstones of the world (2001)
Colour
Colour (General)Red, pink, white, orange, blue, brown
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
TransparencyTranslucent,Opaque
Walter Schumann, Gemstones of the world (2001)
More from other references
Fluorescence & other light emissions
Fluorescence (General)Dull purplish-red
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Crystallography of Coral
Crystal SystemTrigonal
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
HabitDistinctive wavy parallel fibrous structure
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Further Information
Mineral information:Coral information at mindat.org
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