Grandidierite: Gemstone Information

Grandidierite is the One the Most expensive and rare gemstone in the world, and it is one the rarest top 10 gemstone Types in the world, along with gems like jeremejevite, painite, benitoite and taafeite. Grandidierite It forms in the orthorhombic crystal system; it is typically bluish-green in colour and distinctive colour from traces of iron. Gemmy material is translucent to transparent. Fully transparent specimens are ultra rare.
Grandidierite is the most favourite gemstone for gem collectors and love to add their collection, but it has been almost difficult to find. The recent discovery of some gem quality material in Madagascar has now made a few high-quality stones available. While trichroism can usually help distinguish grandidierite from other gems, It has strong pleochroism: dark blue-green, colourless and dark green.

Grandidierite was first discovered in 1902 in Madagascar by Alfred Lacroix, a French mineralogist. Lacroix named the mineral in honor of French explorer and naturalist Alfred Grandidier (1836–1912), the first authority on the natural history of Madagascar.
Sources:
The type locality and many wells understood location is Andrahomana, southwest of Fort Dauphin, southern Madagascar. Other sources that are minor Kachenbere Hills, Malawi; Béjaia, Algeria; Ontario, Canada; Warren County, NY, USA; Tuscany, Italy; Masataka, Surinam; Cuvier Island, brand new Zealand and Norway.
Properties of Grandidierite
Grandidierite is (Mg,Fe2)Al3(BO3)(SiO4)O2 and has provided rather characteristic translucent bluish green or greenish blue elongated anhedral crystals of the orthorhombic system with hardness 7.5 and SG 2.98–3.00. The RI for the alpha, beta and gamma rays is 1.590–1.602, 1.618–1.636, 1.623–1.639 biaxial negative with birefringence 0.039. Grandidierite occurs in aluminous boron-rich rocks and in pegmatites.