See our: marquise jewelry.
A type of finger ring that has a vertical elliptical bezel pointed at both ends and is set with a large gemstone (usually a diamond) or paste, sometimes with a surround of small diamonds, a cluster of diamonds, seed pearls or small gemstones, or a cameo or a jasper medallion made by Wedgwood.
Some examples used as mourning jewelry have enamelling on the bezel in purple or black or enclose under the bezel a miniature, usually of a woman weeping by a willow or urn. Such rings were introduced in the second half of the 18th century.
From: An Illustrated Dictionary of Jewelry, autor: Harold Newman, publishers: Thames and Hudson