CROSSITE

    Class : Silicates
    Subclass : Inosilicates
    Crystal system : Monoclinic
    Chemistry : Na2(Mg,Fe)3(Al,Fe)2Si8O22(OH)2
    Rarity : Common

Crossite belongs to the group of sodium amphiboles, within which it constitutes an intermediate term of the glaucophane - riebeckite series. It is an amphibole of regional metamorphic rocks of low temperature and low and high pressure (green schist and glaucophane blue schist facies respectively); it is also present in eclogites. It was named in honor of the American geologist Charles Whitman Cross. Its crystals are often indistinct, and rarely constitute elongated prisms ; generally, crossite forms lamellar, fibrous, granular or bacillary masses, gray to grayish blue in color.

Main photo : Crossite from Voglau, Salzburg, Austria © Matteo Chinellato

Crossite in the World

Well-known samples come from Custer and Idria (California). Many Japanese localities also provided quality samples. It is still present in beautiful crystals near Shang, in the northwest of Pakistan.

Crossite in France

In France, crossitis is reported in St-Véran (Hautes-Alpes) and St-Jean-de-Maurienne (Savoie).

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 6
Density : 3
Fracture : Sub-conchoidal
Streak : White

TP : Translucent to opaque
RI : 1.640 to 1.670
Birefringence : 0.012
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : Insoluble


Magnetism : Paramagnetic
Radioactivity : None