Okenite: Properties and Occurrences

Okenite (CaSi2O5·2H2O) is a silicate mineral commonly found with zeolites. It is most commonly found within basalt geodes as small white “cotton ball” formations. It is typically found in basalt geodes as small white snowball formations. These formations are made up of clusters of straight, radiating, fibrous crystals that are both bendable and delicate. It also belongs to the calcium silicate hydrates (C-S-H) family, which is commonly found in hardened cement paste. It is written in cement chemist notation (CCN) as CaO•2SiO2•2H2O and abbreviated as CS2 H2.

Okenite was discovered by F. Von Kobell in 1828, and was named after the famed German Botanist, Lorenz Oken. Okenite is usually found in a pale to pearly white color, but can also be seen as yellow and very light blue.

Okenite is a silicate mineral that is usually associated with zeolites. It most commonly is found as small white cotton ball formations within basalt geodes.

General Information

  • Category: Phyllosilicate
  • Formula: (repeating unit) CaSi2O5·2H2O
  • Crystal system: Triclinic
  • Crystal class: Pinacoidal (1)
  • Color: White, may show slightly yellow or blue tint

Properties

This mineral appears to be covered in hair or fuzz, and when touched, it feels similar. The crystal structure of okenite allows it to bend and move, unlike any other crystal you’ve ever seen! Because it’s still a very fragile mineral, don’t bend each crystal too much.

  • Crystal habit: Bladed crystals, typically fibrous
  • Twinning: Lamellar
  • Cleavage: Perfect on {001}
  • Fracture: Splintery
  • Tenacity: Elastic
  • Mohs scale hardness: 4+1⁄2-5
  • Luster: Vitreous, pearly
  • Streak: White
  • Diaphaneity: Transparent, translucent
  • Specific gravity: 2.28 – 2.33
  • Optical properties: Biaxial (-)

Discovery and occurrence

It was named after German naturalist Lorenz Oken (1779–1851) after an occurrence on Disko Island in Greenland in 1828.

Okenite’s most famous locality is in the Indian state of Maharashtra. It is also found in the following countries: Iceland, Greenland, the Faroe Islands, Chile, New Zealand, Ireland, and the United States. Okenite forms near or in association with a variety of Zeolites, Apophyllite, or Prehnite in the majority of these locations.

Minerals associated with okenite include apophyllite, gyrolite, prehnite, chalcedony, goosecreekite and many of the mother zeolites. Okenite is found in India, mainly within the state of Maharashtra. Other localities include Bulla Island, Azerbaijan; Aranga, New Zealand; Chile; Ireland and Bordo Island in the Faroe Islands.