Chalcedony is a translucent variety of quartz, often grayish or bluish-white, valued as a semiprecious stone in the ancient world. John lists it as the third foundation stone in his vision of the New Jerusalem's wall foundations. The twelve foundations display a spectrum of precious and semiprecious stones, each contributing to the city's radiant beauty and representing the glory of God's eternal dwelling place. The specific identification of ancient gemstone names can be uncertain, but chalcedony was known and valued in antiquity.