How to tell the Difference Between Lab Grown diamond and Mined Natural Diamonds?

Since a lab grown diamond appears identical to a mined natural diamond, most jewelers won’t be able to tell the difference. 

(Assuming, of course, that the diamond has no girdle inscriptions). However, jewelers who are also trained gemologists may be able to tell whether a diamond is lab grown diamonds with the aid of a powerful microscope. Still, the only way to be certain is to send it to a gemological laboratory.

So, if you're not a trained/experienced jewelers, you'd better to buy the Loose Lab Grown diamonds which with IGI or AGL

With AGL or IGI Certificate, all information of the Lab diamond are listed in the Certificate. 

AGL is a pioneer in the colored gemstone industry and was the first gemological laboratory in the USA to issue country-of-origin reports.

IGI Certificate Diamond:

IGI Stand for International Gemological Laboratories. IGL certificates online verification. The IGL Diamond Certificate provides a reliable and accurate documentation of a diamond's identity and grade based on the internationally recognized diamond grading system.