It's not the shape (round, oval, pear ... As we know, your engagement ring has 1 carat diamond with the colour F and a VVS1 clarity which if natural would be a stunning gem but as this is lab ...

The RapNet Diamond Index (RAPI™) for 1-carat diamonds — reflecting round, D to H, IF to VS2 goods — decreased 0.5% in December. The index for 0.30-carat diamonds rose 1% as improvements in D to F, VVS ...