Certificates, treatment and buying with confidence

For a fancy colour diamond, the certificate is not paperwork — it is the line between a natural rarity and a treated lookalike worth a fraction of the price.

What the lab actually decides

Two of the report's findings carry most of the weight: the colour origin — whether the colour is natural or has been induced — and the colour grade itself. Both are expert judgements, which is why the trade relies on a small number of laboratories — GIA, IGI and HRD — to make them.

Natural versus treated

• HPHT — high-pressure, high-temperature processing can lighten, deepen or change a diamond's colour.
• Irradiation — a controlled dose mimics nature's greens and blues.
• Coating and dyeing — surface treatments add colour that is not part of the crystal at all.

These are all legitimate products — but only when disclosed. A trustworthy report states "natural," or names the treatment plainly. A treated stone can be beautiful, yet it is worth a small fraction of its natural equivalent, so the distinction is everything.

Reading the report

• Colour origin should read natural for a natural stone.
• Colour grade should match what your eye sees in good light.
• Measurements and the report number should match the stone — many are laser-inscribed on the girdle.

A buyer's checklist

• Insist on a report from GIA, IGI or HRD.
• Confirm the origin reads natural, or that any treatment is named.
• Match the report number to the laser inscription on the stone.
• For a stone with no certificate, treat the colour claim with caution — and ask.

The stone you receive should match its report exactly: colour, weight and number.

Every NFCD stone is graded by one of these laboratories, and what arrives in your hand matches its report to the letter.