Grandidierite

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Grandidierite
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General
Category Nesosilicate
Formula
(repeating unit)
(Mg,Fe2+)Al3(BO3)(SiO4)O2
Strunz classification 9.AJ.05
Dana classification 54.01.01.01
Crystal system OrthorhombicB
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Pbnm
Identification
Color Bluish green
Twinning none
Cleavage Perfect
Fracture Brittle
Mohs scale hardness 7.5
Luster Vitreous, Pearly
Streak White
Diaphaneity Transparent, Translucent
Density 2.976
Optical properties Biaxial (-)
Refractive index 1.583 - 1.639
Pleochroism Visible
2V angle Measured: 24° to 32°, Calculated: 32°
Dispersion strong r < v
References [1][2]

Grandidierite is an extremely rare mineral and gem that was first discovered in 1902 in southern Madagascar. The mineral was named in honor of French explorer Alfred Grandidier (1836–1912) who studied the natural history of Madagascar.[1]

References[edit]