Celsian - Encyclopedia

    Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Monoclinic
    Chemistry : BaAl2Si2O8
    Rarity : Uncommon

Celsian, also called celsianite, is a rare term from the feldspar group in which it forms two incomplete series with orthoclase and hyalophane. It was named in honor of the Swedish astronomer and naturalist Anders Celsius. It is an accessory mineral of contact metamorphic rocks, pyrometasomatic manganese deposits and amphibolites. It forms short to elongated prismatic crystals resembling those of orthoclase, which can show Carlsbad, Baveno and Manebach twins, with a maximum size of 2 cm. It is colorless to whitish, straw yellow, sometimes pink when it contains iron oxides.

Main photo : Celsian from Benallt Mine, Rhiw, Wales, United Kingdom © Christophe Boutry

Celsian in the World

The best celsian crystals come from Rhiw (Wales, United Kingdom), but good samples have been taken from the Langban manganiferous deposit (Sweden), as well as from the metamorphic deposits of Franklin (New Jersey) and Broken Hill (Australia).

Celsian in France

In France, celsian is reported at Mail de la Pique near St-Gaudens (Haute-Garonne) as well as in Arrens (Pyrénées-Atlantiques). 

Right photo : Celsian from Mail de la Pique, Haute-Garonne, France © Jose Miguel Sola Fdez

Twinning and special crystallizations

Simple twins according to the laws of Manebach, Baveno or Carlsbad are known.

Fakes and treatments

No fake identified for this mineral species.

Hardness : 6 to 6.5
Density : 3.10 to 3.39
Fracture : Irregular
Streak : White

TP : Translucent to transparent
RI : 1.580 to 1.596
Birefringence : 0.014
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None

Solubility : Insoluble

Magnetism : None
Radioactivity : None


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