Grandidierite
Real mineral · legendary · (Mg,Fe)Al₃(BSiO₉)
One of the rarest gem minerals on Earth. First described in 1902 from a single locality in Madagascar. Its strong trichroism shifts from colourless to blue-green to dark green depending on viewing angle. Facetable crystals of any size represent extraordinary finds.
Identity
- Formula
- (Mg,Fe)Al₃(BSiO₉)
- Chemical class
- silicate
Crystallography
- Crystal system
- orthorhombic
- Habits
- prismatic, massive
- Fracture
- uneven
Physical properties
- Mohs hardness
- 7.5
- Density
- 2.98 g/cm³
- Luster
- vitreous
- Colors
- blue-green, teal, pale blue
- Streak
- white
- Transparency
- transparent, translucent
Geology
- Origins
- metamorphic
- Host rocks
- pegmatite, gneiss
- Associated minerals
- Kornerupine, Sapphire, Spinel
- Geography
- Madagascar (Tulear only), Sri Lanka, Malawi
Classification
- Rarity
- legendary
- Gem quality
- Yes
Arcane properties
- Affinity
- water, air
- Effects
- scrying, planar travel
- Planar origin
- Material Plane
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