THULITE

    Class : Silicates
    Subclass : Sorosilicates
    Crystal system : Orthorhombic
    Chemistry : Ca2Al3(SiO4)3(OH)
    Rarity : Rare to very rare

Thulite is a fine-grained, pink-hued variety of zoisite, a mineral of the epidote group. Thulite is a mineral of argillaceous limestones and marls that have undergone low-intensity regional metamorphism, more rarely of eclogites or hydrothermalized eruptive rocks. This mineral takes its name from the ancient term Thule, which designated the northernmost coast of Norway where this variety was exploited. The pink hue of thulite results from the replacement of a little aluminum by manganese and rare earths. The crystals are very rare but specimens of 30 mm are nevertheless known. Massive, it is a popular ornamental stone.

Main photo : Thulite from Mjønes Tunnel, Norway © Oivind Thoresen

Thulite from Mjønes Tunnel, Norway © Doug Gardner
Thulite from Mjønes Tunnel, Norway © Michael Krause
37.46 ct thulite cabochon from Norway
35.00 ct thulite cabochon from Norway

Thulite in the World

Thulite crystals of 3 cm are known in Westgard (California) and crystals of 1 cm have been discovered in Mjønes Tunnel (Norway). Large masses of thulite are mined for ornamentation in northern Norway, in the Thule region, at Spruce Pine (North Carolina) and in Namibia.

Thulite in France

In France, thulite is reported in small pinkish decimetric masses at Pontaut-d'Aleu (Ariège).

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 6 to 7
Density : 3.15 to 3.36
Fracture : Irregular to conchoidal
Streak : White

TP : Translucent
RI : 1.696 to 1.718
Birefringence : 0.006 to 0.018
Optical character : Biaxial +
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrofluoric acid

Magnetism : ParamagneticRadioactivity : None