Formation
(1) Magmatic-hydrothermal, through precipitation from copper-rich, low-sulfur fluid solutions in cavities of mafic lavas under reducing conditions.
(2) Sedimentary-diagenetic, through reduction of copper-bearing pore waters in terrestrial red sediments (redbed type) in the presence of organic matter or sulfides.
(3) Secondary, in the cementation zone through reduction of dissolved copper secondary minerals from the oxidation zone (e.g., through tectonic subsidence + rising groundwater).
