See our: eternity rings.
A type of finger ring in the form of a circular band set with a continuous row of gemstones (usually diamonds) of the same size and cut.
It is a type of modem wedding ring set with encircling gemstones. When the gemstones extend only on half of the shank, it is called a 'half--eternity ring'. The stones are secured in a channel setting or in adjacent single-stone collet settings.
Modern examples are usually made of platinum, and sometimes depart from the traditional form by having two or three adjacent rows of stones, each row of different coloured gemstones, and sometimes having the two outer rows extend only halfway around the hoop.
The history of the eternity ring extends back into antiquity, an example being known from Ur 4,000 years ago. In the Elizabethan period some examples were made in the form of an encircling snake swallowing its tail. It is sometimes called an 'alliance ring'.
From: An Illustrated Dictionary of Jewelry, autor: Harold Newman, publishers: Thames and Hudson