How do you tell a lab grown diamond from a natural?

[PureDiamonds]

I've been researching the differences between lab-grown and natural diamonds. All of the 'tells' I am coming across seem to only occur in colored/fancy or fairly included diamonds.

However if you have a D, IF lab-grown, how can you positively confirm that it is lab grown?? Monocrystalline, no fluorescence, birefringence, etc.

 

[Bron357]

Lab grown diamonds are virtually identical in chemical composition to dug from the ground diamonds. The main difference is in their impurities at a molecular level. Type Ia diamonds contain nitrogen atoms and are very common amongst dug from the earth diamonds whereas no lab grown diamonds are type 1a. Lab grown diamonds (colourless) are type IIb, no nitrogen. Obviously you need very sophisticated and expensive equipment to make these observations so currently lab grown diamonds are inscribed as such on their girdle (you need a x30 Loupe to read such inscriptions).
So no standard gemologist testing is going to sort out lab grown from earth found easily.