For Opal lovers, nothing could be better than this Opal engagement ring, set in 14k gold. The band is 5/16 of an inch and tapers down to 1/8 of an inch at the back. It has height, too – with a 5/16 of an inch up off the finger. But forget about that gorgeous band for a moment. The oval stone here is a 6mm round-cut beauty, and this centerpiece is surrounded by 36 diamonds.