Treatments: what is normal, what is not

Heat treatment is industry-standard for rubies, sapphires, and tanzanites. It permanently improves colour and clarity by dissolving inclusions and shifting the crystal lattice. A heated stone is structurally as durable as an unheated one. Disclosure is required by all reputable labs.

Heat is reversible only at temperatures that would destroy the stone itself, so it is considered permanent for practical purposes. Heated stones trade at substantial discounts to unheated stones of equivalent appearance — sometimes 5x to 10x for Kashmir sapphires and Burmese rubies.

Emeralds are almost universally oiled — cedar oil seeps into surface-reaching jardin and improves clarity. Light oiling is acceptable industry practice and stable for decades under normal wear. Heavy oiling or resin filling (Opticon, etc.) is more aggressive and can deteriorate over time, leaving the stone looking worse than the day you bought it. We grade oil intensity (none, minor, moderate, significant) on every emerald certificate.

Irradiation deepens colour in stones like topaz and tourmaline. It is stable when followed by heat, less so otherwise. Lattice diffusion (beryllium or titanium) is a more aggressive treatment that pushes colour through the stone's surface; it is stable but is considered a significant treatment by labs and is priced accordingly.