Sericite, KAl2(OH,F)2AlSi3O10 Potassium Aluminium Fluoro Silicate, is a microcrystalline variety of Muscovite, a mineral belonging to the Mica subfamily of sheet Silicates.  It forms by the alteration of Muscovite by very hot water during extended periods of hydothermal circulation. Since these waters also tend to carry dissolved mineral salts, Sericite is often associated with metal ore deposits such as copper and tin.

Description: A large specimen of Sericite which shows the microcrystalline structure well. Close examination shows the surface to be composed of hundreds of overlaying undulating sheets of mica. Many of these form wave-like structures on the surface. The colours vary from pale yellow, to cream, to dark brown. The combination, coupled with a very bright luster produces a very aesthetic effect.

Location: Strzegom, Slask, Poland.