What is Grandidierite?


Grandidierite is a rare mineral that is often found in Madagascar and Sri Lanka. It’s primarily used as a gemstone and is popular for its bluish-green to greenish-blue color. Due to its rarity, it’s considered one of the most valuable gemstones.

Grandidierite is an extremely rare and valuable gemstone that comes in shades of bluish-green to greenish-blue. Its unique appearance and color make it a popular choice for high-end jewelry and collectors’ items.

Gemstone Properties

Chemical ClassificationInorganic - Borosilicate
ColorPrimarily blue-green, with intense color being the most valuable.
TransparencyTypically transparent to translucent.
OccurrenceMadagascar is the primary source. Other sources are not well-documented due to its rarity.
FormationGrandidierite is found in pegmatites and boron-rich metamorphic rocks.
Mohs Hardness7.5.
Specific GravityApproximately 2.85 - 2.98.
Diagnostic PropertiesTranslucent blue-green.
Chemical Composition(Mg,Fe2+)Al3(BO3)(SiO4)O2
PleochroismStrong; blue, green, and colorless.
Crystal SystemOrthorhombic
Optical PropertiesBiaxial (+)
Refractive Index1.590 - 1.623
Birefringence0.009 - 0.010
2V angleMeasured: 85° to 90°
DispersionNot typically noted due to its color and transparency.