Untreated, Heat Only or Minor Oil? How to Read a Gemstone Treatment Label

October 7, 2026

Untreated no-oil Colombian emerald, 1.82 ct oval, on a black background

Every stone we sell at Roho Jewels has its treatment written on the listing. That line matters more than almost anything else for a coloured gemstone's value, so here is what each label means.

Untreated (no heat, no oil)

The stone is exactly as it came out of the ground, apart from cutting and polishing. Untreated stones are the rarest category and carry a premium. For sapphires you'll often see this called unheated or no heat; for emeralds, no oil. Traditional Jyotish buyers looking for Neelam or Pukhraj usually require an unheated stone. When we sell a stone as untreated, our guarantee is simple: if an independent lab finds any treatment, you get a full refund.

Unheated 14.59 ct icy blue Ceylon sapphire, emerald cut, on a white display stand — Untreated: our 14.59 ct unheated Ceylon sapphire, never heated or treated.

Untreated no-oil Colombian emerald, 0.995 ct oval, on a black background — Untreated: a no-oil Colombian emerald, 0.995 ct.

Heat only

Most sapphires and rubies on the market are gently heated to improve colour and clarity. It's a stable, permanent and widely accepted treatment that has been practised for centuries, and it's how beautiful sapphires and rubies remain affordable. A heated stone needs no special care.

GIA certified royal blue sapphire, 1.65 ct oval, heated — Heat only: 1.65 ct royal blue sapphire, heated as stated on its GIA report.

AGL certified cornflower blue Ceylon sapphire, 1.09 ct oval, heat only — Heat only: 1.09 ct cornflower blue Ceylon sapphire with an AGL report.

Minor oil (emeralds)

Almost every emerald is oiled to soften the look of its natural inclusions. "Minor" is the lightest level, meaning the stone is close to its natural state. Oil can be affected by ultrasonic or steam cleaners and harsh chemicals, so clean oiled emeralds with lukewarm soapy water and a soft brush.

Zambian emerald, 2.51 ct emerald cut, minor oil only — Minor oil: a 2.51 ct Zambian emerald, close to its natural state.

Glass filled

Lower-grade sapphires and rubies can have their fractures filled with lead glass to improve transparency. These stones are real sapphire or ruby, but they are worth far less and need gentle care: no jeweller's torch, no re-polishing, no ultrasonic cleaning. We always label glass-filled stones clearly and price them accordingly.

Lab-grown

A lab-grown stone is not a treatment but a different origin: it is created in a laboratory rather than mined. Lab-grown diamonds are chemically real diamond. We sell a small number of certified lab-grown diamonds, always labelled as lab-grown.

Why we disclose everything

Two stones can look identical in a photo and differ in value by ten times because of treatment. We'd rather you buy once, with full confidence. If a listing doesn't answer your question, message me and I'll tell you exactly what you're buying.