Ultrasonic cleaning may damage which gemstone?

• A. Tourmaline
• B. Diamond
• C. Emerald
• D. Opal

Answer: (A)

Ultrasonic cleaning uses high-frequency vibrations in liquid that create cavitation—tiny bubbles that collapse with enough energy to dislodge dirt but also stress the stone. Stones with brittle crystal structures or internal flaws are most at risk because those flaws can act as crack initiation points where the energy concentrates and cracks propagate. Tourmaline often contains internal fractures and inclusions, and its crystal structure can be prone to cracking under stress. The rapid, localized shocks from ultrasonic cleaning can cause surface chipping or deeper cracks in tourmaline, more readily than in very tough stones like diamond. Emeralds and opals have their own cautions (oil-filled emeralds and water-rich opal faces), but the specific vulnerability from cavitation is most pronounced for tourmaline, making it the best answer.