halotrichite

Halotrichite is a rare, secondary mineral that forms in the oxidation zone of copper deposits. It is named for its characteristic fibrous or acicular habit, which resembles the hair-like structures of halotrichous bacteria. The mineral is typically found in association with other secondary copper minerals such as brochantite, langite, and chrysocolla.

Halotrichite has a chemical formula of Cu4(SO4)(OH)6, indicating it is a copper sulfate hydroxide. It crystallizes in the monoclinic system and is often found as thin, needle-like crystals or as fibrous aggregates. The mineral is typically a bright blue color, but can also be found in shades of green or yellow due to impurities or alteration.

Halotrichite is relatively soft, with a Mohs hardness of 2.5 to 3. It has a specific gravity of approximately 3.2 and is non-fluorescent. The mineral is soluble in water and can be identified by its characteristic blue color and fibrous habit.

Halotrichite is not commonly used as a gemstone due to its softness and tendency to alter. However, it is of interest to mineral collectors and researchers studying the weathering processes of copper deposits. The mineral has been reported from a number of locations worldwide, including the United States, Chile, and Australia.