Topaz gemstone color often produced through irradiation

While topaz is a naturally occurring aluminum silicate mineral, much of the brilliant blue topaz found in jewelry is produced through high-energy irradiation rather than occurring naturally in that hue. In its natural state, topaz is typically colorless or appears in various pale shades.

Color variations in topaz are caused by impurities, element substitutions, or defects in the crystal lattice that change how the stone absorbs light. For instance, some red and pink varieties derive color from chromium atoms. While heat can cause color changes, irradiation is specifically used to transform colorless topaz into blue gemstones.

Chemically, topaz contains fluorine and hydroxide. Despite the use of radiation in the coloring process, the resulting blue gemstones are not radioactive. Topaz is a highly durable mineral, rating 8 on the Mohs scale.