Andradite

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Gemological information for andradite
Color Green: Demantoid, Black: Melanite, Yellow: Topazolite
Crystal Structure Cubic
Refractive Index ~1.89
Durability Good
Hardness 6.5
Treatments Demantoids can be Heated to Improve their Color
Demantoid Localities
  • 1853 - Ural Mountains, Russia. Demantoid first found, identified as green andradite in 1864, named demantoid in 1878 after the dutch diamant due to its adamantine luster and high dispersion. The deposit seemed exhausted at one point but around 1999 production continued and fine stones were found in the years after that. Typical inclusion: the so-called horsetail which is composed of chrysolite fibres.
  • 1997 - Deposit discovered in central Namibia. These stones typically show a yellow to brown secondary hue. Horsetail inclusions are absent. Namibian demantoid garnets have a lower Cr3+ content than the Ural demantoids.
  • 2009 - Antetezambato, Madagascar. Demantoid was found here by fisherman in 2008. Once the news got out in April 2009 thousands of miners came to the area to try their luck. The stones found have brown and yellow undertones. Some curved needle like inclusions have been observed in these stones.
Demantoid2.jpg
Melanite
The black opaque andradite variety is called melanite and has been used in mourning jewelry in the past
Topazolite
The yellow andradite variety. May show chatoyancy
Garnet care
Ultrasonic cleaning Safe
Steam cleaning Safe
Warm soapy water Safe
Chemical attack Avoid
Light sensitivity Stable
Heat sensitivity Stable
Lang Antiques
Lang Antiques