Axinite

 ( Calcium Minerals ) 

Axinite is a brown to violet-brown, or reddish-brown bladed group of composed of calcium aluminium boron-silicon, . Axinite is pyroelectricity and piezoelectric.

The axinite group includes:

• Axinite-(Fe) or ferroaxinite, Ca₂Fe²⁺Al₂BOSi₄O₁₅(OH) iron rich, clove-brown, brown, plum-blue, pearl-gray Handbook of Mineralogy: Ferroaxinite
• Axinite-(Mg) or magnesioaxinite, Ca₂MgAl₂BOSi₄O₁₅(OH) magnesium rich, pale blue to pale violet; light brown to light pink Handbook of Mineralogy: Magnesioaxinite
• Axinite-(Mn) or manganaxinite, Ca₂Mn²⁺Al₂BOSi₄O₁₅(OH) manganese rich, honey-yellow, clove-brown, brown to blue Handbook of Mineralogy: Manganaxinite
• Tinzenite (CaFe²⁺Mn²⁺)₃Al₂BOSi₄O₁₅(OH) iron – manganese intermediate, yellow, brownish yellow-green Handbook of Mineralogy: Tinzenite

Axinite is sometimes used as a gemstone.Tables of Gemstone Identification By Roger Dedeyne, Ivo Quintens p.147

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