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


We offer two types of services –  a verbal assessment or a full report with treatment disclosure & origin opinion for the listed major commercial gemstones:

  • Ruby, Sapphire, Emerald, Spinel, Demantoid, Alexandrite, Paraiba tourmaline, Padparadscha sapphire.

GCS gemstone reports are available for single loose gemstones, gemstone pairs, gemstone sets, and also for mounted jewellery, including items like rings, ear clips, necklaces, brooches, and more, provided that the mounting permits thorough testing.


GCS gemstone reports include the following data based upon our judgment on the day of testing:

  • Report Number - Every report is assigned a distinct numerical identifier. This unique document number plays a crucial role in verifying the authenticity of the report.
  • Date - The date on the report identifies the date when the item was processed for examination at our laboratory.
  • Object Description - A brief description identifies an item being tested
  • Identification - Descriptive identity of gemstone examination. Examined stones of natural formation, are identified as Natural before the items’ name. Items produced from a synthetic crystal, will bear the term Synthetic in front of the name (e.g. Synthetic Ruby). Stones that have undergone rigorous treatment will be marked as Treated.
  • Color Photo - A full color image captured at the time of testing of item. Color and size may vary from the actual item.
  • Shape / Cut - Describes both the shape and the cut of the tested item. Shapes can be round, oval, octagonal, fancy, etc. Cut refers to the facet pattern, e.g. brilliant cut, step cut, polished etc.
  • Color - Describes the spectral hue of the gemstone, e.g. red, blue, green, yellowish-green etc
  • Comment - Describes observations noted on the gemstone such as possible enhancement (e.g. heat-treatment, clarity enhancement using oils or resins, dying etc.). In certain rare cases, determination of enhancement of the tested item is not possible. In these cases we will indicate Treatment undeterminable. Refer to the LMHC Enhancement Disclosure page for further details.
  • Origin Opinion - GCS reports include a geographical origin opinion if such is determinable and requested. A gemstones’ Determination of Authenticity and Country of Origin is based on the testing of the physical and chemical properties of that stone. A conclusion is reached after examining the analysis of the internal characteristics (e.g. inclusions and growth structures) using standard gemmological devices and modern analytical instruments FTIR, UV & PL spectrometers, XRF …. The conclusion as to country of origin, authenticity, and treatment status of gemstones is an opinion of the laboratory based on direct comparisons of the findings with those obtained from the analyses of reference materials and published literature. To the best degree possible, GCS continuously updates this extensive knowledge base. Examined stones that do not produce sufficient data to arrive at an origin opinion will not have such information included.