Aquamarine engagement rings? Absolutely! Diamonds may be a girl's best friend, but Aquamarine engagement rings are a unique, original, and a far more affordable choice. A long time favorite of jewelry designers, aquamarine is the birthstone of March. The diamond-like brilliance of an aquamarine ring is sure to attract attention. Once considered more valuable than diamonds, a peridot ring is a must have. This "gem of the sun" is the birthstone of August and is a beautiful match for the lush green tapestry of late summer.