Gemstone treatments, plainly
Most colored gemstones sold today have been treated in some way after they left the ground. That is normal and not a reason to avoid a stone. What matters is that you know, because a treatment can change the price, how you care for the stone, or both. US law agrees: the Federal Trade Commission’s Jewelry Guides ask sellers to disclose any treatment that affects value or care.
The common ones
Heating. Sapphire, ruby, aquamarine, tanzanite and many others are heated to improve color or clarity. The result is permanent and needs no special care. Heated stones cost less than rare unheated stones of the same look.
Irradiation, usually followed by heating. This is how almost all blue topaz gets its color, from sky blue to Swiss blue to London blue. The color is stable in normal light and wear. Stones are held until any residual radioactivity is below safe limits before they are sold.
Fracture filling and oiling. Emeralds are often oiled, and some rubies are filled with lead glass. These need gentler care: no ultrasonic cleaners, no strong heat.
Diffusion and coating. Color added to or near the surface. It can wear or be polished away, so these stones are priced well below untreated ones.
What our listings say
Each listing has a Treatment line. “None known” means we have no sign of treatment but the stone has not been tested by a lab. When a stone has a lab report, the report is named on the listing. If you need certainty about a specific stone, ask us before you buy.