Axinite

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^[4]
• Axinite-(Mg) or magnesioaxinite, Ca₂MgAl₂BOSi₄O₁₅(OH) magnesium rich, pale blue to pale violet; light brown to light pink^[5]
• Axinite-(Mn) or manganaxinite, Ca₂Mn²⁺Al₂BOSi₄O₁₅(OH) manganese rich, honey-yellow, clove-brown, brown to blue^[6]
• Tinzenite (CaFe²⁺Mn²⁺)₃Al₂BOSi₄O₁₅(OH) iron – manganese intermediate, yellow, brownish yellow-green^[7]

Axinite is sometimes used as a gemstone.^[8]

Gallery

• 
  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 × 3.5 × 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

References

1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
2. Axinite Archived November 19, 2008, at the Wayback Machine. Mineral Galleries
3. Axinite. Mindat
4. Handbook of Mineralogy: Ferroaxinite
5. Handbook of Mineralogy: Magnesioaxinite
6. Handbook of Mineralogy: Manganaxinite
7. Handbook of Mineralogy: Tinzenite
8. Tables of Gemstone Identification By Roger Dedeyne, Ivo Quintens p.147