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Gems Formed in Metamorphic Rocks
Geological context for demantoid, including serpentinite-associated occurrences in Iran. Background research, not a report on the collection.
Learn · Research library
Research library.
Independent publications that inform this site — summarised plainly, linked to the original.
Publications
The library.
Does a horsetail inclusion guarantee Russian origin?
Horsetail inclusions also occur in material from Iran and Italy. Their presence alone does not establish origin.
The Gübelin Gem Project: Garnet
Published garnet specimen data, including demantoid identified as being from Iran. These records concern the specimens studied, not stones on this website.
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These publications provide context. They are not certificates, endorsements or reports on stones presented on this website.
Terms
A short glossary.
- Andradite
- The garnet species of which demantoid is the green variety.
- Dispersion
- The splitting of white light into spectral colours; seen as “fire”.
- Horsetail inclusion
- Fine fibres radiating from a point, characteristic of serpentinite-hosted demantoid.
- Refractive index
- How strongly a gem bends light; demantoid’s is about 1.88–1.89.
- Serpentinite
- A rock formed by alteration of ultramafic rocks; host to demantoid in Iran and Russia.
- Skarn
- Rock formed where hot fluids react with carbonates; host to some demantoid, e.g. Namibia.
See it in a stone.
See how these features appear across our round demantoid.