Grandidierite
Grandidierite
Published: June 2014
Modified: October 2021
Grandidierite is a greenish blue or bluish green mineral named after French explorer and naturalist Alfred Grandidier. The mineral was originally discovered on the southern coast of Madagascar in the Andrahomana area. A new gem quality deposit was found near Tranomaro, Madagascar in 2014.
General Information
Common Name
Grandidierite
Species
Grandidierite
Transparency
Transparent-Translucent
Dispersion
Strength: Strong Fire
Refractive Index
1.590-1.639
Birefringence
0.033- 0.037
Optic Character
Biaxial
Optic Sign
Negative
Polariscope Reaction
Aggregate (AGG), Doubly Refractive (DR)
Fluorescence
SWUV: Inert
LWUV: Inert
LWUV: Inert
Pleochroism
Trichroic, pale yellow to colorless, greenish blue, and blue or greenish blue, blue-green and colorless
Hardness
7-7.5
Streak
White
Specific Gravity
2.85-3.010
Toughness
Good
Inclusions
Apatite, monazite, and zircon crystals, liquid and 2-phase inclusions. Parallel growth planes.
Luster
Vitreous
Fracture
Uneven
Cleavage
Good, Distinct
Chemical Name
magnesium aluminum borosilicate
Chemical Formula
(Mg,Fe)Al3(BO4)(SiO4)O
Crystal System
Orthorhombic
Chemistry Classification
Silicate
Grandidierite Colors
-
Green -
Green -
Blue -
Green
Countries of Origin
Unknown; Madagascar
Care
Normal care