Cheap fake diamond rings are cheap because they’re made with man-made diamonds instead of naturally occurring diamonds.

There are two methods for making synthetic diamonds. The high pressure, high temperature method was the first, and it’s still the mostly commonly used because of its relatively low cost.

The HPHT method uses presses weighing several hundred tons to produce pressure of 5 gigapascals (a unit of measuring pressure) at 1,500 degrees Celsius.

The second method is called chemical vapor disposition, where the stone is grown from a hydrocarbon gas mixture.

There are a couple of ways to tell if a diamond is a fake. The scratch test, where you use the diamond to scratch glass, simply isn’t good enough because diamonds aren’t the only gemstone that can cut glass. Besides, It’s possible to damage a real diamond by scraping it across glass.

Instead, try this: Breathe on the diamond to fog it up. Your stone is real if it the fog disappears immediately. That’s because real diamonds disperse heat instantaneously. If your stone stays fogged for more than four seconds, it’s probably a fake. For valid results, be sure the diamond is completely clean and free of oil or dirt.

The newspaper test is good for loose stones. Place the stone on a piece of newsprint. If the newsprint is clearly readable through the stone, it’s probably a cubic zirconium. Real diamonds scatter light and would make the newsprint look slightly blurry.

The U.V. test can also be helpful. About one third of real diamonds turn fluorescent blue under ultraviolet light while 99% of fake diamonds do not.