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 both pyro-electric and piezo-electric. Pyro-electricity is the ability of certain materials to generate a temporary voltage when they are heated or cooled. Piezo-electricity means electricity resulting from the applied pressure.

Pyro-electricity is different from thermo-electricity. In pyro-electricity, the whole crystal is changed from one temperature to another resulting in a temporary voltage across the crystal. In thermo-electricity, the two sides of the material are kept at two different temperatures resulting in a permanent voltage across the crystal.

The axinite group includes:

Axinite-(Fe), ferro-axinite, iron rich, lilac brown to black

Axinite-(Mg), magnesio-axinite, magnesium rich, pale blue to gray

Axinite-(Mn), manganaxinite, manganese rich, yellow-orange