Rare Madagascar Gems
Grandidierite, demantoid garnet, tourmaline, and other rare species from Madagascar's diverse geology.
Introduction
Beyond sapphire and ruby, Madagascar's diverse Precambrian metamorphic and
pegmatite geology produces an exceptional range of rare collector gemstones.
Grandidierite, a blue-green orthorhombic boroaluminosilicate mineral first
identified in Madagascar in 1902, became available in facetable gem quality only
from the 2000s; Madagascar remains the world's primary source for gem-quality
material, which is strongly trichroic and hardness 7–7.5. Demantoid garnet
(andradite variety) with high dispersion was found in the early 2000s and adds
Madagascar to the short list of demantoid sources alongside Russia and Namibia;
some stones contain chrysotile-like "horsetail" inclusions. Tourmaline includes
Cu-bearing neon elbaite (Paraíba-type), rubellite, indicolite, and chrome
tourmaline. Chrysoberyl, including some alexandrite, colour-change pyrope-
spessartine garnet, spessartine, rhodolite, and kornerupine complete a collector
portfolio unique in its breadth. Madagascar continues to yield new discoveries,
maintaining its status as the world's most diverse single-island gem source.
[1][2]
Grandidierite
Madagascar's signature rare gem:
Discovery & Source
- First identified: 1902 in Madagascar [1]
- Gem quality: Only recently available (2000s)
- Primary source: World's main supplier
- Rarity: Among rarer collector gems
Characteristics
- Colour: Blue-green to greenish-blue
- Pleochroism: Strong trichroic effect
- Hardness: 7-7.5 (suitable for jewellery)
- Crystal system: Orthorhombic
Market
- Collector gem with growing awareness
- Prices rising as awareness increases
- Limited supply maintains value
- Not yet mainstream market
Grandidierite Discovery
Demantoid Garnet
Fine green garnet production:
Discovery
- Found in early 2000s
- Significant find for collector market
- Adds to worldwide demantoid sources
- Competes with Russian, Namibian material
Characteristics
- Fine green colour possible
- Good dispersion ("fire")
- Horsetail inclusions in some material
- Andradite garnet variety
Tourmaline
Madagascar's diverse tourmaline:
Varieties Available
- Multiple colours produced
- Some neon blue-green (Paraiba-type copper-bearing)
- Rubellite (pink-red) varieties
- Chrome tourmaline (green)
- Indicolite (blue)
Paraiba-Type
- Copper-bearing tourmaline found
- Neon colours similar to Brazilian/African
- Smaller production than Mozambique
- Collector interest
Market
- Growing production
- Good quality available
- Competitive pricing
- Various colours for diverse market
Additional Species
| Gem | Notes |
|---|---|
| Chrysoberyl | Including some alexandrite colour-change |
| Spinel | Red and pink varieties available |
| Rhodolite garnet | Fine purple-red material |
| Spessartine garnet | Orange varieties |
| Labradorite | Spectrolite-quality available |
| Rose quartz | Star rose quartz noted |
| Sphene | High dispersion; collector interest |
| Kornerupine | Rare; some gem quality |
Colour-Change Gems
Madagascar produces several colour-change varieties:
Alexandrite
- Chrysoberyl variety
- Some fine colour-change material
- Competes with Brazilian, Sri Lankan
- Collector interest
Colour-Change Garnet
- Pyrope-spessartine varieties
- Blue-green to red/purple change
- Related to East African material
- Exceptional specimens highly valued
Collector Significance
Why Madagascar matters for collectors:
- Species diversity: Exceptional range of gem types
- Rare species: Primary source for several unusual gems
- Quality potential: Fine material in many species
- Discovery ongoing: New finds continue
- Value: Often excellent for quality received
References
- ↑ 1. Schumann, W. (2009). Gemstones of the World (4th ed.). Sterling Publishing. ISBN: 978-1-4027-6829-3.
- ↑ 2. Kissin, A.; Murzin, V.; Karaseva, O. (2021). 'Horsetail' Inclusions in the Ural Demantoids: Growth Formations, Not Chrysotile. Minerals, 11(8), 825. DOI: 10.3390/min11080825.