Eritiste

Eritiste is a cobalt arsenate mineral with the chemical formula Co3(AsO4)2·8H2O. It is a secondary mineral that forms in the oxidation zones of cobalt-bearing ore deposits and is particularly noted for its distinctive pink to red color. The name derives from the Greek erythros, meaning red, in reference to its hue.

Eritiste crystallizes in the monoclinic system and commonly occurs as slender prismatic crystals, though it is more often found as radiating aggregates, crusts, or masses. Its color ranges from bright pink to crimson, with a pink streak and a vitreous to pearly luster on fresh surfaces. It is relatively soft, with a Mohs hardness typically reported around 3 to 4, and has a specific gravity near 3.

This mineral forms in the oxidation zones of cobalt-rich deposits and is frequently associated with other cobalt minerals such as cobaltite and skutterudite, as well as with various arsenates. As a hydrated cobalt arsenate, eritiste can serve as an indicator mineral for cobalt mineralization, though it is not a primary cobalt ore.

Handling considerations: Because eritiste contains arsenic, proper handling is advised and dusty materials should be avoided.

See also: Arsenate minerals, cobalt minerals, erythrite.