Here's some advice for you men:  Never walk up to a woman and ask, "Are those real?"  That includes when you're just innocently asking about her diamonds! 

In all seriousness, worrying about whether or not you're purchasing the real thing, whether from a respected jeweler in the mall or when shopping elsewhere, is actually a commendable attitude.  After all, even the smallest of diamonds are going to cost you hundreds of dollars and many view them as an investment, not just a piece of jewelry, so of course being worried about whether or not they're the genuine article is going to cross everyone's mind.

In some cases, people actually are after fake diamonds.  Cubic zirconias, or manmade stones, are very difficult to tell from the real thing at least to the untrained eye.  Some see absolutely nothing wrong with saving themselves some money by purchasing these if all they're after is the flash and brilliance of the stone.  Of course, the difficulty in telling apart the fake from the real may save you some dollars but will make it all the more difficult to avoid being fooled.  And for most, they want real diamonds in that engagement ring or earrings that will be a Christmas gift or whatever other piece they're shopping for.

So how can you tell the fake diamonds from the real thing, short of getting your degree in gemology?  There are some things you can look for.  One, notice the setting of the stone.  Most fakes are held by low-quality metal settings.  See if the setting is a mix of metals or if it's pure platinum or gold.  Second, take a close look at the stone itself.  Diamonds are the hardest stone on earth and should never have a scratch anywhere on them. 

Real stones will have a certificate from the Gemological Institute of America (GIA) to ensure its authenticity.  Be sure you're offered this certificate when you're looking at the stone.  Also, have your diamonds appraised by an independent appraiser, preferably one that is a member of the American Society of Appraisers (ASA).

Unfortunately it is getting harder and harder to tell the real diamonds from the fake, considering the improved methods that producers use every single year.  This is good for those who just want a stone with some flash and sparkle, but bad for those who want to invest in the real thing.  Consider purchasing your stones only from a reputable jewelry store that is well-known and that has been in business for some time now.  Avoid buying anything at flea markets and resale shops or thrift stores, no matter how well advertised they are or how good looking the piece is.  By being careful, you're sure to be safe rather than sorry.

Insist on a diamond certification before purchasing for investment purposes.  It will tell you the stone's carat weight, its color and clarity, and its flaws if any.  If the seller is unwilling or unable to supply a certification with the diamond then he or she may not be telling the truth about the diamond.  After all, when you want to sell the diamond, the new owner will want a certification from you.