A style of setting in which many small gemstones (usually calibré or faceted diamonds, sometimes turquoise and half-drilled pearls) are set very close together in a mass so as to cover the entire piece and to conceal the metal. The stones (often backed with foil) are secured in holes drilled through the metal base and held in place by burrs pressed down over the edges of the stones. It is a style used for brooches, pendants, etc. that seek to emphasize the massed effect rather than any individual stone. On some dome-shaped jewels, the stones must be of graduated sizes, diminishing in concentric circles from the central stone, to permit accurate close spacing.
From: An Illustrated Dictionary of Jewelry, autor: Harold Newman, publishers: Thames and Hudson