Andradite

Big Photo

Demantoid
Russia
2.09 carats
© Palagems

Andradite is a species of the garnet group. It was named after the Brazilian mineralogist José Bonifácio de Andrade e Silva (1763–1838).

Andradite Gemstones by Colour

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

Andradite Gemstones by Size

This table shows distribution of Andradite 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:0.34 cts
Heaviest:25.89 cts
Average:4.40 cts
Total photos:36
Do you have a larger Andradite? Why not upload a photo?
0.34ct to 2.90ct2.90ct to 5.45ct5.45ct to 8.01ct8.01ct to 10.56ct10.56ct to 13.12ct13.12ct to 15.67ct15.67ct to 18.23ct18.23ct to 20.78ct20.78ct to 23.34ct23.34ct to 25.89ct
General Information
A variety or type of:Garnet Group
Varieties/Types:
Demantoid - A green variety of andradite.
Melanite - A black variety of andradite.
Topazolite - A yellow-brown variety of andradite.
Chemical Formula
Ca
 
3
Fe
 
2
(SiO
 
4
)
 
3
Arthur Thomas, Gemstones (2009)
Photos of natural/un-cut material from mindat.org
Physical Properties of Andradite
Mohs Hardness6.5 to 7
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Specific Gravity3.70 to 4.10
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Cleavage QualityNone
Arthur Thomas, Gemstones (2009)
FractureConchoidal
Arthur Thomas, Gemstones (2009)
Optical Properties of Andradite
Refractive Index1.88 to 1.94
Walter Schumann, Gemstones of the world (2001)
More from other references
Optical CharacterIsotropic
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) Anomalous double refractionMore from other references
Dispersion0.057
Arthur Thomas, Gemstones (2009)
ChatoyancyReddish brown variety may show chatoyancy and, in other cases, iridescence caused by twinning planes
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Colour
Colour (General)Black, colourless, green, yellow-green, yellow
Arthur Thomas, Gemstones (2009)
Causes of ColourYellow-green, Fe3+ in octahedral coordination. Green (demantoid), Cr3+ in octahedral coordination. Yellow (topazolite), to black (melanite), various charge transfer processes and dispersed ion absorption involving Fe and Ti. Multicolors, diffraction
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTransparent,Translucent
Arthur Thomas, Gemstones (2009)
LustreSubadamantine,Vitreous
Arthur Thomas, Gemstones (2009)
Fluorescence & other light emissions
Fluorescence (General)Inert
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Crystallography of Andradite
Crystal SystemIsometric
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
HabitDodecahedral, trapezohedral
Arthur Thomas, Gemstones (2009)
Geological Environment
Where found:In skarns from contact metamorphosed impure limestones or calcic igneous rocks; in chlorite schists and serpentinites; in alkalic igneous rocks, then typically titaniferous.
Anthony et al, Handbook of mineralogy (2001)
Further Information
Mineral information:Andradite information at mindat.org
Significant Gem Localities
Canada
 
  • Québec
    • Chaudière-Appalaches
      • Les Appalaches RCM
        • Saint-Joseph-de-Coleraine
Wilson (2007)
Wilson (2007)
Iran
 
  • Kerman
    • Baft County
Laurs (2002)
Italy
 
  • Lombardy
    • Sondrio Province
      • Valtellina
Zang (2008)
Japan
 
  • Nara
    • Yoshino district
      • Tenkawa village
Hainschwang and Notari (2006)
Madagascar
 
  • Diana
    • Ambanja
      • Antsakoamanondro
Danet (2009)
Mali
 
  • Kayes Region
    • Cercle de Bafoulabé
      • Commune Diakon
Brightman and Tunzi (1995)
Mexico
 
  • Sonora
[var: Demantoid]
Myanmar
 
  • Mandalay Region
    • Pyin-Oo-Lwin District
      • Mogok Township
        • Kyatpyin Central
Ted Themelis (2008) Gems & mines of Mogok
Namibia
 
  • Erongo Region
    • Dâures
      • Tubussis Farm 22 (Tubussis; Tubusis; Tubessis)
[var: Demantoid] Laurs (2002)
Russia
 
  • Chelyabinsk Oblast
    • Verkhny Ufaley
      • Ufaley District (Ufalei District)
        • Korkodin
[var: Demantoid] Korchevskaya (2006)
  • Sverdlovsk Oblast
    • Yekaterinburg
[var: Demantoid] Zang (2008)
Sri Lanka
 
  • Sabaragamuwa Province
    • Ratnapura District
      • Ratnapura
Copyright © Jolyon & Katya Ralph 1993-2019. 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.