The answer is no.
You can find Zircons (fake diamonds/diamond replacements/glass diamonds) in a quality that even an expert might have a hard time telling them apart.
It is especially hard when the diamond is inlayed in jewelry.
What methods are used to check if a diamond is fake or not?
In modern times when technology is extremely advanced, experts can identify if a diamond is fake or not with no doubt:
Diamond weighting – it is possible to know if a diamond is fake by its weight.
Different kinds of Zircons weight twice as much a real diamond weight which makes it easy to spot the fake.
An expert will know to spot when the size of the diamond and its weight does not match although its is common to use real diamonds as a comparison.
Diamond Transparency – an expert can evaluate a diamond by placing it on a colorful surface.
If the transparency is low the diamond is fake.
If the transparency is high, we are looking at a real diamond.
Gemological Equipment – nowadays we have advanced technological equipment that can determine in absolute certainty if a diamond is fake therefore it is possible to send the diamond to a gemological lab when in great doubt.
Loss Of Spark – is another way to evaluate diamond in retrospect.
After a year Zircons, which are fake diamonds, lose their spark and seem lifeless.
If the modification is found in reasonable time it might be possible to use the authorities to correct the injustice caused by selling a fake diamond as a real one.
The best way to avoid purchasing a fake diamond is to buy diamonds and jewelry from companies that provide gemological certificates and to check beforehand the credibility and reputation of said company.