From Wikipedia, the free encyclopedia
Jump to: navigation, search
Axinite – Deposit Topotype, France
Category Sorosilicates
(repeating unit)
(Ca,Fe,Mn)3Al2BO3Si4O12OH or Ca2(Fe,Mn)Al2BSi4O15(OH)
Strunz classification 9.BD.20
Crystal system Triclinic
Pinacoidal class
Color Reddish brown to yellow to colorless. Blue, violet, grey.
Crystal habit Tabular, wedge shaped crystals
Crystal symmetry Triclinic
H-M Symbol: (1)
Space group: P1
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 [1][2]

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-(Fe) or ferroaxinite, Ca2Fe2+Al2BOSi4O15(OH) iron rich, clove-brown, brown, plum-blue, pearl-gray[3]
  • Axinite-(Mg) or magnesioaxinite, Ca2MgAl2BOSi4O15(OH) magnesium rich, pale blue to pale violet; light brown to light pink[4]
  • Axinite-(Mn) or manganaxinite, Ca2Mn2+Al2BOSi4O15(OH) manganese rich, honey-yellow, clove-brown, brown to blue[5]
  • Tinzenite, (CaFe2+Mn2+)3Al2BOSi4O15(OH) iron – manganese intermediate, yellow, brownish yellow-green[6]

Axinite is sometimes used as a gemstone.[7]



  1. ^ Axinite. Mineral Galleries
  2. ^ Axinite. Mindat
  3. ^ Handbook of Mineralogy: Ferroaxinite
  4. ^ Handbook of Mineralogy: Magnesioaxinite
  5. ^ Handbook of Mineralogy: Manganaxinite
  6. ^ Handbook of Mineralogy: Tinzenite
  7. ^ Tables of Gemstone Identification By Roger Dedeyne, Ivo Quintens p.147