Cyanotrichite

A copper aluminium sulfate mineral, Cu₄Al₂(OH)₁₂SO₄·2H₂O, also known as lettsomite, very similar to halotrichite, and a member of the same group. However, it is much rarer. It forms velvety aggregates of extremely fine fibres and radial aggregates.

The main deposits are Cap la Garrone in the Var (France), Romania and Arizona (USA). Because of its beautiful colouring, lettsomite is very popular with collectors.