Euclase - Encyclopedia

    Class : Silicates
    Subclass : Nesosilicate
    Crystal system : Monoclinic
    Chemistry : BeAlSiO4(OH)
    Rarity : Rare

This rare aluminum beryllium nesosilicate is found in some pegmatites and chloritoschists (sometimes in alpine fissures as a decomposition product of beryl). Unalterable, it is sometimes concentrated in alluvium. Its name comes from the Greek eu (good) and klasis (breaking), alluding to its excellent cleavage. The euclase is always cristallsié in prime elongated and striated longitudinally, often tabular and rich in faces. It is transparent to translucent, colorless, yellowish, pale blue-green to blue, and has a high hardness (7.5). It is a mineral occasionally cut as a gem and sought after by collectors.

Euclase in the World

The most beautiful euclase crystals come from Zimbabwe (Miami), where the superb dark blue individuals exceed 5 cm, Tanzania (7 cm crystals), Boa Vista and Dom Bosco (Minas Gerais, Brazil), where superb centimetric gemmy ones are associated with imperial topaz. The Galacha emerald deposit (Colombia) also yielded beautiful blue-green specimens (main photo). In Europe, the geodes of the Bavarian granites yielded magnificent colorless crystals of 2 cm.

Euclase in France

This mineral is not present in the French underground.


No twinned crystals for this species.

Fakes and scams

No fake recorded for this species.

Hardness : 7.5
Density : 2.99 to 3.1
Fracture : Conchoidal
Streak : White

TP : Transparent to translucent
IR : 1.652 to 1.671
Birefringence : 0.019
Optical character : Biaxial
Pleochroism : Visible
Fluorescence : Red

Solubility : Insoluble

Magnetism : None
Radioactivity : None