Quarry
A quarry is a small square or diamond-shaped pane of glass, set in lead. The word comes from the French carré, meaning square. Windows made of quarries, often laid on the diagonal so that they form a diamond lattice, are one of the oldest and most familiar forms of leaded light.
Quarries were used in medieval and Tudor houses and churches, where a window might be made of clear quarries with a few painted or coloured pieces set among them. They returned in the nineteenth century with the Gothic Revival and the Arts and Crafts movement, and are still common in cottages, porches and doors.
A window of diamond panes is often called a diamond quarry window, and the proportion of the diamond, long and narrow or nearly square, helps to date it.