How to compare two gemstones responsibly

Two sapphires, similar weight, similar price – which is the better purchase? The answer rarely lies in a single feature. A responsible comparison looks at several properties and relies on verifiable information.

Step 1: compare like with like

Compare stones of the same species and variety. A ruby and a red spinel can look similar, yet they are different materials with their own pricing logic.

Step 2: check identity and report

Both stones should have a report from a recognised laboratory, ideally the same laboratory. Laboratories sometimes use different terms, for example for colour names such as "Royal Blue" or "Pigeon Blood".

Step 3: compare treatment

An untreated stone and a heated stone are not equivalent, even if they look alike. Read the exact wording.

Step 4: colour under the same light

Look at both stones side by side, under the same light and against the same background. Photographs from different sources are unsuitable for comparing colour.

Step 5: clarity and inclusions

Consider whether inclusions are visible to the eye and whether they affect durability – not only whether they exist.

Step 6: cut, weight and dimensions

A well-cut stone looks livelier. Compare the dimensions to judge the visible size.

Step 7: origin and documentation

Origin and provenance influence value. They only count, however, if they are documented.

What does not belong in the comparison

• Superlatives without evidence, such as "unique" or "investment grade"
• Promises about future value
• Photographs without information on the light source

In brief

A responsible comparison looks at several features side by side and relies on verifiable information. Compare stones of the same species, under the same light and ideally with reports from the same laboratory. Promises about future value do not belong in the comparison.

At NOBILITH

In the collection, the information for every stone is structured in the same way: laboratory report, treatment, weight, dimensions and origin opinion appear in the same place. This allows stones to be compared directly. On request we show two stones side by side under the same conditions during a consultation.

Sources

• CIBJO: The Gemstone Book
• GIA: Gem Encyclopedia, quality factors of coloured gemstones