網上商店買鑽石 is very dangerous.
If you want to buy diamond, I'd rather you to pay more to buy a diamond which is with good quality in shops like 周生生,周大福,TSL,or even Tiffany.
Mabelle is also one of the choices.
It is better to buy a diamond in big shops because there will be certificate and you can change it if you don't like the style or you can change a bigger diamond by giving back the old diamond and paying more.