I’m looking to purchase a 1.1 ct diamond. I’ve read that when buying a 1.1 ct diamond always buy one that is just slightly above or under 1.1 ct (for example: 1.05 ct or 1.15). Is this true even when purchasing from Blue Nile?
The “just under” advice doesn’t apply at every tenth of a carat break point. The price jumps generally follow the Rapaport diamond report groups (0.01 – 0.03), (0.04 – 0.07), (0.08 – 0.14), (0.15 – 0.17), (0.18 – 0.22), (0.23 – 0.29), (0.30 – 0.39), (0.40 – 0.49), (0.50 – 0.69), (0.70 – 0.89), (0.90 – 0.99), (1.00 – 1.49), (1.50 – 1.99), (2.00 – 2.99), (3.00 – 3.99), (4.00 – 4.99), (5.00 – 5.99). The biggest jumps happen at the round numbers 0.5, 1, 1.5, 2, etc.
1.05 and 1.15 are both within the 1.00-1.49 bucket, so you won’t see any massive deals by gaming the off-carat weight. However, the cost-efficiency frontier tends to be determined around 1.1 – 1.3ct (maximizing the distance between the 1ct and 1.5ct spikes), so you might find better value in those ranges. You can just look at the curves to see this.
