Aragonite

Big Photo

Sardinia, Italy
11.70 carats

Aragonite is named after the Aragon region, Spain, where pseudo-hexagonal twinned crystal forms were first recognized.

Aragonite is a polymorph of calcite, having the same chemical composition but a different physical structure. When aragonite is heated to 400°C it will convert to calcite.

Aragonite occurs in compact, granular, massive or radially fibrous forms. Crystals are often twinned and form pseudohexagonal prisms. They are usually white or colourless but may have brown, grey, green or violet hues. Transparent crystals of aragonite are found in many places, particularly in Bohemia, Spain and the north of England. Massive material is found in horizontal layers. A layered sedimentary marble-like material is sometimes referred to Mexican Onyx and is used for carvings and ornamental objects.

Aragonite forms the basis for many organic gems, such as coral, mother-of-pearl and pearl.

Aragonite Gemstones by Colour

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

Aragonite Gemstones by Size

This table shows distribution of Aragonite 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:6.45 cts
Heaviest:22.82 cts
Average:11.96 cts
Total photos:10
Do you have a larger Aragonite? Why not upload a photo?
6.45ct to 8.09ct8.09ct to 9.72ct9.72ct to 11.36ct11.36ct to 13.00ct13.00ct to 14.64ct14.64ct to 16.27ct16.27ct to 17.91ct17.91ct to 19.55ct19.55ct to 21.18ct21.18ct to 22.82ct
General Information
Chemical Formula
CaCO
 
3
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Photos of natural/un-cut material from mindat.org
Physical Properties of Aragonite
Mohs Hardness3.5 to 4
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Specific Gravity2.93 to 2.96
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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TenacityBrittle
Arthur Thomas, Gemstones (2009) Very brittle
Cleavage QualityDistinct
Arthur Thomas, Gemstones (2009)
FractureSub-Conchoidal
Arthur Thomas, Gemstones (2009)
Heat SensitivityModerate
Arthur Thomas, Gemstones (2009)
Optical Properties of Aragonite
Refractive Index1.525 to 1.686
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Optical CharacterBiaxial/-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Birefringence0.155
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) DoublingMore from other references
PleochroismStrong
Arthur Thomas, Gemstones (2009)
DispersionLow
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)White, yellowish, reddish, greenish, bluish, violet. Commonly banded
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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TransparencyTransparent,Translucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreVitreous
Arthur Thomas, Gemstones (2009)
Fluorescence & other light emissions
Fluorescence (General)Common orange or cream
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Fluorescence (Short Wave UV)Green-white, pink, white
Arthur Thomas, Gemstones (2009)
Fluorescence (Long-Wave UV)Pink, white
Arthur Thomas, Gemstones (2009)
Crystallography of Aragonite
Crystal SystemOrthorhombic
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
HabitFrequently shows pseudohexagonal habit which is caused by combination and twinning
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Geological Environment
Where found:Typical deposits occur at hot springs, in cavities in volcanic rocks and in cave formation.
Arthur Thomas, Gemstones (2009)
Further Information
Mineral information:Aragonite information at mindat.org
Significant Gem Localities
Canada
 
  • Alberta
    • Lethbridge
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 385
Czech Republic
 
  • Ústí Region
Namibia
 
  • Erongo Region
Peru
 
  • Puno
Copyright © Jolyon & Katya Ralph 1993-2018. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.