When testing for imitation or fake diamonds, the thermal conduction test uses an instrument like the GIA GEM pocket diamond tester, which measures the heat conductivity of a diamond. A metal probe is pressed against a facet of the diamond to obtain a reading.

This test does not work against moissanite, which will pass this test. There are other ways to test for moissanite however - like the double facet test.

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: