Which instrument measures both thermal and electrical conductivity to differentiate diamonds and simulants?

• A. Thermal Tester
• B. Refractometer
• C. Multi-Testers
• D. Polarimeter

Answer: (C)

The main idea is using both thermal and electrical conductivity to separate diamond from simulants. Diamond stands out because it conducts heat extremely well but does not conduct electricity. A instrument that can test both properties at once—the thermal conductivity test and the electrical conductivity test—will give a distinctive result for diamond: high thermal conductivity with no electrical conduction. Many simulants do not show this exact combination, so they won’t match both tests. A Thermal Tester only checks how heat moves through the stone, which can be inconclusive if a simulant has similar heat transfer. A Refractometer looks at how light bends to determine refractive index, which isn’t related to conductivity. A Polarimeter measures optical rotation, also unrelated to conductivity. The Multi-Tester combines both conductivity tests, providing the most reliable differentiation between diamond and its common simulants.