Natural pearls are hugely expensive - some as much as hundreds of dollars for just one pearl! That's fairly expensive for a ring but what if you were buying enough for a necklace? Now you're looking at, most likely, over a thousand dollars minimum. When you're making that kind of investment, it's important to be sure of what you are buying. One easy way to know is the name: faux, fake, artificial, synthetic, man made - if you see these in the description you'll know right away. There may be cases though, where you may not be able to tell so easily, and that is where these six tests will come in handy!
Density is one way to check for authenticity. If you are able to see the pearl(s) in person, try picking them up! Real pearls should be fairly heavy for their size. This is because they will have a thick layer of nacre whereas most fakes will be glass with a few coats of mother of pearl on top. Very light pearls are automatically fake - however, this gets a little trickier when they are heavy, as cultured pearls, well made synthetic pearls, and natural pearls will be much closer in weight and density.
The next test is to try exposing your pearls to sunlight. You can also use a bright indoor light. What you should do is pick up the pearl and look at it with your back to the light. First of all, you're checking for the luster - you should be able to almost see your reflection if the quality is high. Secondly, this will let you see all the color variations. This is easier when you are checking multiple pearls against each other. Natural pearls will not match each other exactly unless they are quite costly.
If you're still not sure, try the tooth test. A lot of gemologists seem to recommend this but I don't have any experience with it so be careful. This involves running the pearl very lightly over your teeth. Real pearls should feel fairly gritty, while fakes should feel much smoother. This is because the nacre wasn't formed naturally. The problem with this test is that it will separate natural, non-cultivated pearls from fakes but won't separate fakes from cultured pearls, as they have a thin layer of nacre.
You could also try some form of destructive test. I don't recommend these at all but I feel I should include them for completion's sake. Destructive tests involve cutting the pearl open so you can take a look at the core. You will be able to tell how much nacre there is, and if the core is made of glass, you have a fake on your hands. Obviously this is a last resort - I can't see any reason why I would want to destroy something so valuable, myself.
Magnification will let you see the surface of the pearl in greater detail. Synthetic pearls will be more smooth. Natural or cultured pearls will have ridges or slight imperfections that may or may not be visible to the naked eye.
Finally, you can have your pearls x-rayed. This is the most reliable test you can perform. You will need a (certified) gemologist to take a look. Once done he/she will be able to tell you everything you need to know including whether the pearl is natural uncultured, cultured, or fake, as well as the thickness of the nacre. If you have any doubts at all after the previous tests, this is your best bet. It's well worth the cost when you think of how much money you could lose.
In summary, the six ways to spot fake pearls are checking density, the sunlight test, tooth test, destructive test(s), magnification, and x-rays. Please remember that it is important to contact a gemologist if you still have doubts. There are some very well-crafted synthetic pearls on the market (Swarovski comes to mind) that pride themselves on being as close to nature as possible. I hope this helps and good luck buying your pearls.
