paratacamite

Paratacamite is a copper oxychloride mineral with the chemical formula Cu2Cl(OH)3. It is a rare secondary mineral, meaning it forms as a result of weathering and alteration of primary copper minerals. Paratacamite is typically found in arid to semi-arid environments, often associated with copper deposits. It is characterized by its emerald green to dark green color and often occurs as fibrous or acicular crystals, though massive forms are also observed.

The mineral is named after the Atacama Desert in Chile, where it was first discovered. It is isostructural with atacamite, meaning it has the same crystal structure but a different chemical formula. However, paratacamite is often considered a polymorph of atacamite, meaning it has the same chemical composition but a different crystal structure. Despite their similar appearance, subtle differences in their X-ray diffraction patterns distinguish them.

Paratacamite is a relatively soft mineral with a Mohs hardness of 3 to 3.5. It has a specific gravity of around 3.75 to 4.25. It is insoluble in water but can be dissolved in acids. Due to its rarity and often small crystal sizes, paratacamite is not of significant economic importance as a copper ore. However, it is of interest to mineral collectors and geologists studying mineral formation processes in oxidizing copper environments. Its presence can indicate specific conditions of alteration and weathering at copper-rich sites.