Langite
>
Langite is a rare hydrated copper sulfate mineral, with hydroxyl, found almost exclusively in druses of small crystals. It is formed from the oxidation of copper sulfides, and was first described in specimens from Cornwall, United Kingdom. It is... Wikipedia
Crystal class: Domatic (m); (same H-M symbol)
Crystal habit: Crystals scaly, or as crusts; earthy
Crystal system: Monoclinic
Formula mass: 488.32 g/mol
Formula (repeating unit): Cu4(SO4)(OH)6·2H2O
Luster: Vitreous, crusts silky
Solubility: Insoluble in water, easily soluble in dilute acids or NH4OH