Which property do standard diamond testers primarily measure?

• A. Thermal conductivity
• B. Electrical conductivity
• C. Magnetic properties
• D. Refractive index

Answer: (A)

Thermal conductivity is what standard diamond testers rely on to distinguish diamonds from most imitators. The tester uses a small heated probe that touches the stone and measures how quickly heat flows away from the probe into the gem. Diamond’s lattice structure and strong covalent bonds let it conduct heat extremely well, so heat is drawn away rapidly and the tester reads a response that signals a diamond. Stones like cubic zirconia, glass, or other common simulants don’t transfer heat as efficiently, so the probe temperature changes more slowly and the tester indicates not diamond. Be aware that some materials, such as moissanite, can also conduct heat quite well, which means basic testers can sometimes misidentify them as diamonds; in practice, additional methods are used to confirm.