Unlike in the old days, Dayekh says, recommended retail prices are set for the different grades and are regularly updated by AWDC or GIA industry associations.

A standard monocle, with 10 times magnification, is required for examining diamonds.

"If you are looking for very high-grade diamonds, a microscope would be better, because the standard monocle would not detect tiny flaws on those," says diamond wholesaler Chu Xiao.

Some diamonds also have a laser code in them that corresponds with their certificate number, but this is no guarantee of worth, because these codes can be faked. You are safer with a trustworthy retailer.

Chu, who examines hundreds of diamonds daily, says there are two kinds of false diamonds customers need to aware of.

One is a synthetic or laboratory-grown diamond. Chemically speaking, it has the same structure as a natural one. The only difference is shown on the certificate - HPHT for high pressure high temperature.

The other kind of adulterated diamond is one whose color has been improved by chemical methods. Again, a certificate should specify this.

If a customer has bought one of these "lemon diamonds" believing it to be natural, there is no consumer association or official bureau to file complaints with. The AWDC suggests customers return to the retail store.

Finally, Qi Haojie, vice-president of China's biggest online diamond store Kela.com, also advises owners of diamond rings to have them "serviced" annually by jewelers to make sure the diamond is secured to the metal setting.