Dickite is a phyllosilicate clay mineral, with an identical composition as kaolinite, nacrite, and halloysite, but with a different crystal structure (polymorph).

Its chemical composition is Al₂Si₂O₅(OH)₄. It occurs with other clays and requires x-ray diffraction for its positive identification. Dickite is an important alteration indicator in hydrothermal systems as well as occurring in soils and shales.

References

• Dickite mineral data from mindat.org
• Webmineral data
• Dickite stability PDF