The windowpane oyster (Placuna placenta) is a bivalve marine mollusk in the family of Placunidae. They are edible, but valued more for the shells and pearls. The shells have been used for thousands of years as a glass substitute because of their durability and translucence. More recently they have been used in the manufacture of decorative items like chandeliers and lampshades. In this use the shell is known as capiz. Shells are also used as raw materials for glue, chalk, and varnish.