Your gemstone is treated. Almost certainly.

The right question isn’t "if," but "how" 

Gemstone treatment isn’t the exception—it’s the norm in modern jewellery: by industry estimates, over 90% of coloured stones set in jewellery have undergone a process to enhance colour, clarity, or durability. Some of these methods have been practised for centuries, are explicitly recognised by international standards, and make stones accessible that would otherwise remain rare collector’s pieces. The difference between a legitimate and a questionable practice, therefore, isn’t the existence of treatment, but its stability over time and the extent to which it has been disclosed to the buyer. 

Three categories—no more

Every stone on the market fits squarely into one of three categories, and the right price depends entirely on which category the stone in front of you belongs to. The first is the stone untreated: rare, significantly more expensive, and impossible to guarantee without a certificate issued by an independent gemological laboratory. A seller who claims “untreated” without putting a document on the table is, effectively, saying nothing. 

The second category, which covers the overwhelming majority of the market, is the stone treated by accepted methods. Here, “accepted” means two things at once, not just one: the method is stable over time and it is disclosed in writing. If either of these two conditions is missing, the stone no longer belongs in this category. 

The third category includes stones treated by unstable methods or substituted materials. Their existence isn’t a problem in itself—some have their decorative role, at their price point. The problem appears when they’re sold at the prices of the first two categories.

Gold Pendant Birthstone July - Ruby

What’s accepted in international trade

The CIBJO* international standard, which the European gemstone trade follows, assigns each treatment a code and a mandatory disclosure phrasing. The four methods below are considered legitimate precisely because their results are stable and predictable over time.

The rule worth remembering is that “accepted” doesn’t mean “no effect on price.” An untreated sapphire can be worth several times more than a heated one of the same size, colour, and clarity. Treatment doesn’t disqualify the stone; it sets its price category.

What should put you on alert

At the other end are methods that radically change the balance between what you see and what you pay. The most common is lead-glass filling, typical for ruby: the result is a composite stone, not a ruby—and the difference isn’t semantic. Such material deteriorates on contact with lemon juice or everyday cleaning products and can be destroyed by a simple jeweller’s repair, and its real value is a fraction of a natural ruby’s. Diffusion concentrates colour in a surface layer that can be lost with repolishing. Dyeing is unstable to light, perspiration, and solvents, and coating with a coloured layer scratches and wears off with use. Add to these reconstituted materials—stone powder bound with resin and sold as solid stone, common with turquoise, amber, and lapis—and, in clear cases of deception, material substitution: dyed howlite presented as turquoise, glass as quartz, green glass as emerald.

Language warns you first

You don’t need instruments to make the first check—just read carefully how the stone is described. The CIBJO standard explicitly forbids the term “semiprecious”, considered misleading, as well as fanciful geographic names assigned to artificial materials, such as “Brazilian emerald” for green glass. The treatment must be written with the same visibility as the stone’s name, not hidden in an asterisked footnote. The words “natural,” “genuine,” and “authentic” have no place next to a synthetic or composite material, and synthetics must be clearly preceded by “synthetic” or “lab-grown”—hinted at is not enough. Finally, “natural stone” doesn’t answer the treatment question: a stone can be both perfectly natural and heavily treated.

Gold Ring Love Story - Sapphire & Diamonds 

What to do, concretely, before you pay

The first filter is price, which remains the best treatment detector: a three-carat ruby offered for a few hundred RON is not an untreated ruby but a composite stone or an imitation—no matter how convincing the description. 

The second is the paperwork—the treatment must appear on the invoice or on the product sheet, and for an important purchase it’s worth requesting an independent lab certificate, not one issued by the seller.

The third, and most revealing, is the seller’s answer to three questions asked in this order: is it treated and by what method, is the treatment permanent, and how do I care for it. A seller who doesn’t know the answer is, almost always, a seller who didn’t ask their supplier.

Silver Ring Birthstone Golden August - Peridot 

How this information changes your decision

Once you know the treatment, you know which price category the stone should fall into—and the difference between a heated and an unheated sapphire isn’t cosmetic; it’s a multiple. More importantly, you’ll know how to choose based on how you’ll wear the jewellery: an oiled, filled, dyed, or coated stone works beautifully in a pair of earrings or an occasionally worn pendant, but for a ring worn daily—especially an engagement ring—the risk of degradation rises significantly. Care follows from this too: oiled, filled, dyed, or coated stones must not be cleaned with ultrasonics or steam, and should not be exposed to solvents, cleaning products, or heat—a single piece of guidance that saves more jewellery than any warranty card. And in the long run, a stone with declared and documented treatment can be appraised, insured, and resold; one without a history can’t even be estimated correctly.

Pocket checklist

☐  I explicitly asked if the stone is treated and by what method

☐  The treatment is written on the invoice or on the product sheet

☐  I know whether the treatment is permanent or requires upkeep

☐  The price is coherent with the declared treatment type

☐  I know how to clean the jewellery and what to avoid

☐  For important purchases: I have an independent lab certificate

A properly disclosed treatment doesn’t reduce a jewel’s value—it makes it verifiable. At Indira, every stone is described with its actual material and treatment, so the decision is entirely yours.

*CIBJO is the World Jewellery Confederation (Confédération Internationale de la Bijouterie, Joaillerie, Orfèvrerie)