Precious Gemstones
How to read a gemstone report
Carat, colour, clarity, cut and treatment, in plain language.
Coloured stones are not graded like diamonds. There is no single scale, and the terms on a report mean different things for different species. Here is what matters.
Colour is the biggest driver of value in almost every coloured stone. A vivid, evenly saturated colour can be worth many times a pale or overly dark one of the same weight. Judge it in daylight if you can.
Carat is weight, not size. A carat is 0.2 grams. Because species differ in density, a one-carat sapphire is physically smaller than a one-carat emerald. That is why we publish millimetre dimensions on every listing: they tell you how large the stone will actually look.
Clarity runs from IF (internally flawless) through VVS, VS, SI and I1. What counts as acceptable depends on the species. An emerald with visible inclusions can still be a fine stone; a sapphire at the same clarity would not be.
Cut covers both the outline (oval, cushion, pear) and how well the stone was proportioned. A well-cut stone returns light evenly across the face rather than showing a dark window in the middle.
Origin can carry a premium — Colombian emerald, Burmese ruby, Kashmir sapphire — but origin alone never makes a stone good. Colour and clarity still decide.
Treatment is the one to read carefully. Heating is standard, stable and accepted across the trade. Oiling is normal for emerald. Fracture filling, diffusion and dyeing all affect value materially and must be disclosed. We state the treatment on every product page, and we say what it means for wear and cleaning.
Colour is the biggest driver of value in almost every coloured stone. A vivid, evenly saturated colour can be worth many times a pale or overly dark one of the same weight. Judge it in daylight if you can.
Carat is weight, not size. A carat is 0.2 grams. Because species differ in density, a one-carat sapphire is physically smaller than a one-carat emerald. That is why we publish millimetre dimensions on every listing: they tell you how large the stone will actually look.
Clarity runs from IF (internally flawless) through VVS, VS, SI and I1. What counts as acceptable depends on the species. An emerald with visible inclusions can still be a fine stone; a sapphire at the same clarity would not be.
Cut covers both the outline (oval, cushion, pear) and how well the stone was proportioned. A well-cut stone returns light evenly across the face rather than showing a dark window in the middle.
Origin can carry a premium — Colombian emerald, Burmese ruby, Kashmir sapphire — but origin alone never makes a stone good. Colour and clarity still decide.
Treatment is the one to read carefully. Heating is standard, stable and accepted across the trade. Oiling is normal for emerald. Fracture filling, diffusion and dyeing all affect value materially and must be disclosed. We state the treatment on every product page, and we say what it means for wear and cleaning.