Art Deco 2.12ct M/SI1 Old Mine Brilliant Cut Diamond Engagement RingA wonderful Antique Art Deco Diamond Engagement Ring, which we date to approximately 1920. Set with a wonderful 2. 12ct Old Mine Cut Diamond which has been certified by GIA as M SI1. Although graded as an M colour, the diamond faces up white. Old Mine Cut Diamonds are rare and prized for their fire over their brilliance; this fire is achieved through the relatively high crown by comparison to modern brilliant cut diamonds. You can see in our video