KCa₄Si₈O₂₀(F,OH).8H₂O

This sample of apophyllite is displayed in the Smithsonian Museum of Natural History. Apophyllite is a potassium calcium silicate with the composition KCa₄Si₈O₂₀(F,OH).8H₂O. This gem sample is 15.4 carats and is from Poona, Maharashtra, India.

Mindat treats apophyllite as synonymous with fluorapophyllite.