When testing for imitation or fake diamonds, the closed-back test can be used if the diamond's bottom half is enclosed in the setting or is otherwise blocked from view. In a normal ring setting, the bottom of the diamond is at least partially visible.

A completely closed back setting may indicate that the diamond is fake. For example, a rhinestone with a foil back can be used to simulate a diamond. However, some antique diamond jewelry used solid backings with foil to increase the brilliance of the diamond.

Don't care if it's fake? Modern-day fake diamonds such as cubic zirconia (CZ) or moissanite are hard to tell from the real thing and can offer good value. Check out the links below if you're interested in buying fake diamonds: