Which handheld tool is commonly used to test a diamond's thermal conductivity?

• A. Diamond tester
• B. Refractometer
• C. Spectroscope
• D. Microscope

Answer: (A)

Testing how a material conducts heat is a direct way to identify real diamond versus imitators. Real diamonds have an exceptionally high thermal conductivity because of their strong, tightly bonded crystal structure. A handheld diamond tester uses a small heated probe and gauges how quickly heat moves away from the contact point. If the stone behaves like diamond, the device will indicate a diamond reading; if not, it will indicate not-diamond or a much lower reading. This direct measurement of heat transfer makes it the most practical quick-screen tool for this purpose.

Other instruments measure different properties. A refractometer checks how light bends through the stone to estimate refractive index, which helps differentiate some diamonds from simulants but isn’t about heat transfer and can be fooled by certain imitations. A spectroscope analyzes light emission or absorption lines to identify elements or impurities, which is informative but not about thermal conductivity. A microscope lets you inspect surface features and inclusions, valuable for grading and identification, but it doesn’t assess how the stone handles heat.