A silicate mineral with composition essentially (Cu,Al)₂H₂Si₂O₅(OH)₄·nH₂O; iron, and more rarely manganese, may substitute for copper. Although acicular monoclinic crystals have been reported, the wide variation in the composition of analyzed specimens suggests that chrysocolla is a hydrogel or gelatinous precipitate rather than a well-crystallized mineral. This suggestion is reinforced by the fact that x-ray diffractions are weak and ill defined. The mineral characteristically occurs in impure amorphous-to-cryptocrystalline crusts and masses with conchoidal fracture.