[A_D_E_P_T]

> With close microscopic examination of inclusions and defects, yes you probably can.

With good laboratory instrumentation, you might be able to distinguish between them -- i.e. note that they're not perfectly identical, that they are distinguishable -- but, unless you are an expert, you would be unable to tell which of the two is the natural stone.

So, practically speaking, it doesn't matter.

[s0rce]

Yes, you need to know which features are evidence of mined vs. synthetic/lab grown. Although there is equipment now preloaded with software that can discriminate. I think its based on photoluminescence.