16.14.02: Achroite
- Page ID
- 4343
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Achroite Tourmaline | |
---|---|
Chemical composition | Complex borosilicate |
Crystal system | Trigonal |
Habit | Prismatic |
Cleavage | None |
Fracture | Conchoidal |
Hardness | 7- 7.5 |
Optic nature | Uniaxial - |
Refractive index | 1.62 - 1.64 |
Birefringence | 0.014 - 0.040 |
Dispersion | Low, 0.017 |
Specific gravity | 3.01 - 3.11 |
Lustre | Vitreous |
Pleochroism | Strong |
NaLi2.5 Al6.5 (BO3)3O18(OH)4
Figure \(\PageIndex{1}\): Achroite Crystal, Pakistan
Achroite is a the colorless variety of tourmaline which is usually (but not always) elbaite.