The Carat Weight of Princess Diana's Aquamarine Ring • The exact carat weight of Princess Diana's aquamarine ring is unknown, but it is estimated to be around 30 carats. The emerald-cut stone is quite large and is set in a simple yellow gold band, allowing the gemstone to be the focal point of the ring. • The aquamarine stone is flanked by small diamonds, which add a touch of sparkle to the ring's design.