• +44 (0)207 491 4777
  • contact@gcslab.co.uk
  • 30 New Bond Street, London W1S 2RN



We offer full reports on loose diamonds over 0.25ct.

The report will detail an assessment of the 4Cs of diamond quality – carat weight, colour, clarity, and cut – as outlined in the CIBJO diamond book.
Diamond reports on stones over 0.25ct are accompanied by a plot diagram.

We also specialise in synthetic diamond identification.

Diamond Type Analysis

Determination of diamond type – Ia, Ib, IIa or IIb.

Variety of testing services to determine diamond authenticity, natural vs. synthetic, natural vs. treated, or identify specific treatments.

Colored Diamond Grading Report

Full quality assessment, color grade and clarity plot.

Identifies natural vs. treated color.

In order to determine whether a diamond is of natural or artificial colour, the following investigations are routinely performed on loose stones:

  • Observation with a binocular microscope in dark field, transmitted light, polarized light, and immersion
  • FTIR spectroscopy to determine the type of diamond (type IaA, IaA/B, IaB, Ib, IIa, IIb)
  • UV-visible-near-infrared spectroscopy of the diamond
  • Raman Photoluminescence spectroscopy of the diamond.