Mineral Guide · Mineral
Cadwaladerite is a hydrated aluminium chloride hydroxide known from oxidised and evaporitic environments, including burning coal dumps.
Cadwaladerite is a hydrated aluminium chloride hydroxide known from oxidised and evaporitic environments, including burning coal dumps.
The reference formula is Al5(H2O)3(OH)12·n(Cl,H2O). Cadwaladerite belongs to the halides and crystallises in the cubic system. Mindat reports an isometric structure with a large unit cell and tiny cubic crystals, although much material is amorphous or massive. The variable chlorine and water content should be retained in the formula rather than replaced by a false fixed composition.
Typical colours include white, pale yellow and colourless. For small or complex mineral species, crystal size, transparency, lustre and matrix association are often more diagnostic than colour alone.
Cadwaladerite forms in or is associated with near-surface oxidising processes, evaporitic settings, fumaroles and coal fires. Important documented localities include Poland, Chile and other unusual chloride-rich environments. A precise mine or geological setting is preferable to a broad country label when it is known.
Cadwaladerite is best treated as a labelled reference or collector specimen. Protect fragile crystals from impact and humidity changes. Arsenic-, cadmium-, lead-, thorium- and selenium-bearing minerals should not be cut, ground or used in jewellery; wash hands after handling and keep them away from food and children.
Reviewed by NotOnlyRocks Editorial Team
Last reviewed: 21 August 2026
Looking for Cadwaladerite?
Send us a request and we will try to find a suitable specimen for you.
Request Cadwaladerite