Okenite - Encyclopedia

    Class : Silicate
    Subclass : Inosilicate
    Crystal system : Triclinic
    Chemistry : Ca5Si9O23. 9H2O
    Rarity : Uncommon


Okenite is a spectacular calcium silicate, mainly present in geodes and basalt cavities, in which it accompanies zeolites (apophyllite, gyrolite, laumonite, etc.), prehnite and calcite. It was named in honor of the German naturalist Lorenz Ocken. Its morphology is characterized by extremely fine needle-like crystals which group together to form spiky balls ("sea urchins" or "cotton balls") or radiate tufts. Transparent to translucent, with a vitreous luster, okenite is colorless to white, sometimes slightly yellow. It is a mineral that has no particular use, it is only intended for mineral collectors.

Okenite in the World

The most remarkable deposits are in India, at Poona and in the Khandivali quarries near Mumbai, which yielded subspheric aggregates of extremely fine needle crystals constituting superb balls bristling with crystalline points and exceeding 5 cm in diameter, currently the best specimens in the world. The Jeffrey mine (Abestos, Canada) also provided centimetric tufts of okenite, but less spectacular than the Indian samples. This mineral is also reported in Scottish, American and Czech basalt geodes, but in specimens of lower quality.

Okenite in France

This mineral is not present in the French underground.

Twinning

Existing but invisible to the naked eye.

Fakes and scams

Okenite is always naturally white or slightly yellow in color. It is frequently dyed in various colors (most often canary yellow or green, but also sometimes red or blue and potentially any color) in order to facilitate its sale. These treatments having been widely denounced, they have become rare today on the market.



Hardness : 4.5 to 5
Density : 2,28 to 2,33
Fracture : Fibrous
Trace : White




TP : Translucent to transparent
IR : 1.512 to 1.542
Biréfringence : 0,003 to 0,010
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None


Solubility : Slowly turns into silica gel in acids

Magnetism : None
Radioactivity : None