The only way to make sure that a diamond is real is to have it inspected by a professional. But knowing some of the basics can allow the common person to weed out some of the lesser imitations.

What are fake diamonds usually made of? The most common material is cubic zirconia. Most of the times it's offered as alternative to diamonds and jewelers rarely attempt to pass it off as a real diamond. The next most common material is crystal: cheap and non-durable. Then there's moissanite, a rare mineral that looks like diamonds, has totally different properties and is sometimes more expensive. Here are some of the basic ways in which real diamonds differ from fake ones. Also, to enhance your diamond inspecting abilities, it's a good idea to study up on the so-called four Cs of diamonds. These are: color, clarity, cut and carat, and they are the four things that San Diego jewelers look at to determine the quality of a stone.

Setting Quality
Diamonds are rare and expensive, so you'd expect them to be set with care and skill into equally precious metals. If a stone is loosely set, crooked, or set into a cheap looking metal ring or necklace, chances are it's a fake.

Though they are not impervious to damage, diamonds are the hardest naturally occurring material on earth, and it takes a lot to knick them. If a stone has excessive scuffs and scratches, it's probably not a real diamond.

Rainbow Reflections
If a stone reflects rainbow light, it's not a diamond. Real diamonds have light refraction qualities that manifest as white and gray reflection.

Transparency Test
This test requires a loose diamond. Take the diamond, flip it upside down and place it atop a newspaper. If you can read the print, it means the stone is a fake. This is because real diamonds have certain light properties that make them not entirely transparent, so you shouldn't be able to read the print through them.

Fog Test
Diamonds disperse heat very rapidly, so if you exhale on a diamond, the fog caused by your breath should disappear immediately. If it linger there awhile, it means the diamond is a fake.