tortuosite

Tortuosite is a rare copper- and aluminum-rich silicate mineral. The name derives from its tortuous, twisted crystal habit, which can form interwoven fibrous aggregates or bent crystals.

Chemically, tortuosite exhibits a variable composition dominated by copper and aluminum, with silicon and oxygen forming silicate frameworks. Hydration may occur in the structure, and trace elements can vary by locality. Because of its variable composition, a single, fixed formula is not universally applied.

Crystals are typically slender, acicular prisms or fibrous bundles; color ranges from green to brown-green; the luster is vitreous to silky; the hardness is variable and usually on the lower side of the Mohs scale; streak is light.

Occurrence is in hydrothermal ore deposits and contact metamorphic environments, often in copper-rich contexts. Tortuosite is commonly found with other copper minerals and silicates.

Naming and classification: The mineral was named for its twisted morphology; it is generally described as a silicate mineral. Type material and detailed locality information are documented in mineralogical references.

See also: List of minerals; Glossary of mineralogy; Copper minerals.