The Gemological Science International (GSI) has detected undisclosed lab-grown diamonds (LGD) in jewellery pieces featuring natural brown diamonds, raising concerns over the authenticity of mixed-diamond jewellery.

Utilising advanced instruments, including Fourier Transform Infrared Spectroscopy, DiamondView imaging and Raman spectroscopy with liquid nitrogen cooling, GSI found that several jewellery items contained LGDs mixed with natural stones across a range of hues – from near colourless with faint brown tones to fancy dark brown.

The findings reaffirmed the laboratory’s previous research, which showed that LGDs can effectively replicate a wide spectrum of natural colours.

The discovery comes at a critical time when the global jewellery trade has increasingly been promoting off-colour natural diamonds like brown and champagne as distinctive and affordable alternatives to white diamonds.

“As the industry embraces natural brown diamonds, it is essential to safeguard their integrity in the marketplace,” said Debbie Azar, president and co-founder of GSI, highlighting the importance of rigorous screening protocols and transparent disclosure practices to protect both industry stakeholders and consumers, and to support the industry’s efforts in promoting off-colour natural diamonds with trust and transparency.