Axinite
| Axinite | |
|---|---|
Axinite – Deposit Topotype, France
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| General | |
| Category | Sorosilicates |
|
Formula (repeating unit) |
(Ca,Fe,Mn)3Al2BO3Si4O12OH or Ca2(Fe,Mn)Al2BSi4O15(OH) |
| Strunz classification | 9.BD.20 |
| Crystal system | Triclinic |
| Crystal class | Pinacoidal (1) (same H-M symbol) |
| Space group | P1 |
| Identification | |
| Color | Reddish brown to yellow to colorless. Blue, violet, grey. |
| Crystal habit | Tabular, wedge shaped crystals |
| Cleavage | Good on {100} |
| Fracture | Conchoidal |
| Mohs scale hardness | 6.0–7.5 |
| Luster | Vitreous |
| Streak | White |
| Specific gravity | 3.18–3.37 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.672–1.693 nβ = 1.677–1.701 nγ = 1.681–1.704 |
| Birefringence | δ = 0.011 |
| Pleochroism | Strong |
| References | |
Axinite is a brown to violet-brown, or reddish-brown bladed group of minerals composed of calcium aluminium boro-silicate, (Ca,Fe,Mn)3Al2BO3Si4O12OH. Axinite is pyroelectric and piezoelectric.
The axinite group includes:
Axinite is sometimes used as a gemstone.
Clove-brown axinite crystals to 2.3 cm set atop matrix from the West Bor Pit at Dalnegorsk, Russia
Chloritized bladed crystals of Axinite forming on Adularia from the Swiss Alps
Tinzenite on Calcite, 4.5 x 3.5 x 3 cm. Wessels Mine, Kalahari manganese fields, Northern Cape Province, South Africa
Manganaxinite (Axinite-(Mn)), with sharp curving crystals to 4 cm. West Bor Pit at Dalnegorsk, Russia
faceted axinite, 1.02ct, Brazil
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