Grandidierite
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.
| Chemical Classification | Inorganic - Borosilicate |
| Color | Primarily blue-green, with intense color being the most valuable. |
| Streak | White |
| Luster | Vitreous. |
| Transparency | Typically transparent to translucent. |
| Occurrence | Madagascar is the primary source. Other sources are not well-documented due to its rarity. |
| Formation | Grandidierite is found in pegmatites and boron-rich metamorphic rocks. |
| Diaphaneity | Transparent |
| Cleavage | None |
| Mohs Hardness | 7.5. |
| Specific Gravity | Approximately 2.85 - 2.98. |
| Diagnostic Properties | Translucent blue-green. |
| Chemical Composition | (Mg,Fe2+)Al3(BO3)(SiO4)O2 |
| Pleochroism | Strong; blue, green, and colorless. |
| Crystal System | Orthorhombic |
| Optical Properties | Biaxial (+) |
| Refractive Index | 1.590 - 1.623 |
| Birefringence | 0.009 - 0.010 |
| 2V angle | Measured: 85° to 90° |
| Dispersion | Not typically noted due to its color and transparency. |