A circle on a circle with a round diamond has all the symbolism you could want to express purity and simplicity. Uncluttered design puts the focus on a small, but very real diamond with its attendant story. (It doesn't have to be big to transmit the message.)
Shank 3 mm wide x 1.5 mm thick is substantial, yet not clunkky.
Bezel is 4 mm in diameter and 2 mm thick which holds the stone securely and protects the fragile edges.