Navette

Navette is another term to describe a marquise shaped gemstone or jewelry contour. Pointed at both ends with equally curved sides, the term navette shape usually refers to the contour or outline of a gemstone, such as a marquise shaped cabochon, rather than a faceted gemstone.
French Diamond and Enamel Navette Shaped Ring, c.18th Century.

French Diamond and Enamel Navette-Shaped Ring, c.18th Century.