Axinite Explained

Axinite
Category:	Cyclosilicates
Boxwidth:	200px
Formula:	or
Imasymbol:	Ax^[1]
Strunz:	9.BD.20
System:	Triclinic
Class:	Pinacoidal (same H-M symbol)
Symmetry:	P
Color:	Reddish brown to yellow to colorless. Blue, violet, grey.
Habit:	Tabular, wedge shaped crystals
Cleavage:	Good on
Fracture:	Conchoidal
Mohs:	6.0–7.5
Luster:	Vitreous
Refractive:	nα = 1.672–1.693 nβ = 1.677–1.701 nγ = 1.681–1.704
Opticalprop:	Biaxial (−)
Birefringence:	δ = 0.011
Pleochroism:	Strong
Streak:	White
Gravity:	3.18–3.37
References:	^[2] ^[3]

Axinite is a brown to violet-brown, or reddish-brown bladed group of minerals composed of calcium aluminium boro-silicate, . 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]

Notes and References

1. Warr. L.N.. 2021. IMA–CNMNC approved mineral symbols. Mineralogical Magazine. 85. 3. 291–320. 10.1180/mgm.2021.43. 2021MinM...85..291W. 235729616. free.
2. http://mineral.galleries.com/Minerals/Silicate/AXINITE/AXINITE.htm Axinite
3. http://www.mindat.org/min-440.html Axinite
4. http://rruff.info/doclib/hom/ferroaxinite.pdf Handbook of Mineralogy: Ferroaxinite
5. http://rruff.info/doclib/hom/magnesioaxinite.pdf Handbook of Mineralogy: Magnesioaxinite
6. http://rruff.info/doclib/hom/manganaxinite.pdf Handbook of Mineralogy: Manganaxinite
7. http://rruff.info/doclib/hom/tinzenite.pdf Handbook of Mineralogy: Tinzenite
8. Tables of Gemstone IdentificationBy Roger Dedeyne, Ivo Quintens p.147