In its 150 years of existence, GSI entered into Gem Testing as an aid to render public service during mid sixties. From a humble beginning it has grown into a leading center of gem testing in the country instilling consumer confidence among one and all .

The Gem Testing Laboratory of GSI at Central HeadQuarters, Kolkata assumes a special significance with the booming gemstone business getting mixed up with synthetics, simulants and imitation stones .GSI provides commercial service for identification, authentication and certification of the gemstones. The Mineralogical Report is prepared based on the non-destructive analysis of the gemstones. It comprises essential physical and optical constants along with internal inclusion pattern to arrive at the name of the mineral and its gem variety.
The report also indicates a qualitative assessment of the gemstone based on 4 ‘Cs’ (Cut, Carat weight, Colour and Clarity). Special characters like spectroscopic result, optical effects and external flaws are mentioned under the heading ‘Other Characters’ of the report.

The laboratory, which was started in 1962, boasts of having all the conventional gem testing instruments like Electronic balance with automatic specific gravity determination kit, Refractometer, Table spectroscope, Polariscope, UV lamps, Stereo binocular microscope with immersion scope, Magnavision, Dialite, Fibre optic light, Thermo diamond probe etc in addition to the newer version of petrological microscope with micro photography. Miscellaneous gem testing instruments include Chelsea Colour Filter; Dichroscope; Calcite type (with light attachment); Leveridge Gauge; Moe’s Gauge; Hot wire Device; Fibre Optic Illuminator.

On an average more than 600 stones per month are tested and mineralogical reports generated in GTL, Kolkata.

Other Gem testing facility centres at GSI

• Petrology Division, Central Region, Nagpur
• Petrology Division, Southern Region, Hyderabad
• Petrology Division, North-Eastern Region, Shillong

Upcoming Gem testing facilities

• Stereo Binocular Microscope with digital micro-vision attachments
• Mobile Gem testing laboratory (Portable & comprehensive unit for outside assignments)