Stability is a gem's resistance to damage from heat, light and chemicals.
In more detail
Corundum is stable in normal wear, but boric acid powder can etch it. Sudden temperature changes can crack amethyst, and strong light can fade it. Heat can extend fractures in emerald and alter its fillers. Filled and dyed stones need more care than untreated or heated ones.
On a grading report
Labs may add a care note, for example that a filler is unstable to heat and chemicals.
Related terms
- Durability: Durability is a gem's ability to resist scratching, breaking, and damage from heat, light or chemicals. It has three parts: hardness, toughness and stability.
- Lead-glass filling: Lead-glass filling is a treatment that fills fissures and cavities in corundum, mostly ruby, with high-lead glass to hide them.
- Emerald oiling: Emerald oiling is filling an emerald's fissures with a colorless oil to make them less visible.
- Irradiation: Irradiation is exposing a gem to artificial radiation to change its color. Heating sometimes follows, to modify the color further.
- Amethyst: Amethyst is the purple variety of quartz. Iron in the crystal, together with natural radiation, causes its color.