If you buy an emerald anywhere in the world, the odds are overwhelming that it has been oiled. This is not a scandal and it is not a defect of Colombian stones in particular. It is how the trade has worked for centuries. What separates an honest purchase from a bad one is whether anyone told you.
Why emeralds are oiled
Emeralds form under conditions that leave them with internal fissures — the trade calls the pattern jardin, garden. Many of those fissures reach the surface. Filling them with a colorless oil or resin makes them far less visible, because the filler has a refractive index close to that of the stone.
The treatment changes what you see. It does not change what the stone is.
The degrees
- None. Rare, and priced accordingly. A genuinely untreated emerald of good color is an unusual object.
- Minor. The most common description on good commercial stones.
- Moderate. Still perfectly sellable, at a lower price.
- Significant. Heavy filling. The stone can look excellent and cost a fraction of what an equivalent-looking untreated stone would. That is fine if you know.
What it means for you, practically
Oil is not permanent. Over years, with heat, ultrasonic cleaners, solvents or steam, it can dry out or escape, and fissures that were invisible become visible again. This is reversible: a jeweler can re-oil the stone. But it is the reason emeralds should never go into an ultrasonic cleaner and should be washed with lukewarm water and mild soap.
Resin fillings behave differently from oil and are harder to redo. It is fair to ask which was used.
Why the declaration matters more than the treatment
Two stones can look identical in a display case and differ by a large multiple in price, and the difference is often exactly this. A seller who does not raise the subject is either untrained or counting on you not to ask.
At Kingdom Emeralds the treatment is written on every certificate, including when the answer is none. A stone whose treatment we have not yet established does not go on display.
Would you rather settle it in person, with the stones in front of you? We are in the Edificio Pombo, open every day from 10:00 am to 7:00 pm.
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