What is a common treatment for blue sapphire?

• A. Irradiation
• B. Dyeing
• C. Heating
• D. Coating

Answer: (C)

Heat treatment is the common method used to enhance blue sapphires. When sapphires are heated at high temperatures, color and clarity can improve because certain color centers change and rutile silk that dulls the blue is dissolved or redistributed. The result is a deeper, more even blue that remains stable through normal wear, which is why this method is widely accepted and routinely applied in the trade.

Other treatments exist, but they’re less common for blue sapphires. Irradiation can alter color in some stones, but it’s not the standard practice for producing blue sapphires and often requires special certification. Dyeing would introduce color from an external source and is not durable or reliably detectable in high-quality stones. Coating is a surface treatment that can wear away, making it less desirable for precious gems.