How To Tell If A Diamond is Color Treated
ASSAY GUIDE
How to check if a diamond's color is treated
Two natural diamonds can be $160,000 apart in price. Here is how to know which one you're looking at.
$20,000
Treated color, natural diamond
$180,000
Natural color, untouched
Four things to check
- Ask the seller directly. "Is this color 100% natural, or has it been treated?" Get the answer in writing.
- Read the lab report. Find "Color Origin" on the GIA (or equivalent) certificate. It will say Natural or Treated, sometimes naming the method, such as Irradiated or HPHT.
- Check the wording of the color grade. Look for "Fancy" before the color, like Fancy Yellow or Fancy Vivid Yellow. No "Fancy," just Light Yellow or Very Light Yellow, means a low-saturation stone on the normal scale, worth far less regardless of treatment.
- No certificate, no deal. There is no reliable way to detect color treatment with the naked eye. It requires lab spectroscopy. If a diamond has no certificate, or the certificate doesn't clearly state color origin, don't buy it until it does.
"A treated diamond is still a real, natural diamond. It's simply had its color enhanced, and that's disclosed on paper, not hidden."
Why this happens: a diamond that comes out of the ground with a color nobody wants can be put through HPHT, high pressure and high temperature, which permanently shifts the color. It's a legitimate part of the market. The only problem is when a treated stone is sold as untreated.