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Certification being the main service of ZGTL, which broadly issues two types of reports - identification and diamond grading. Each and every stone under test is examined by gemologists using the standard gemological equipment. Therefore, every report issued is based on immense gemological experience of the gemologists. The report format however varies depending on the type of category under which the certification has been carried out. Identification reports are issued for gems in following whichever form.
1. Loose Rough - well-formed crystals or broken, with or without a polished surface, transparent to opaque,
2. Loose Cut in any style - pre-form, faceted, cabochon, bead - drilled /undrilled.
3. Set in jewellery / in a decorative piece - open or close back setting.
4. Carvings.
5. Beads strung on a thread / wire.
Testing is carried out by following the pre-determined criteria strictly, although the tests to be performed largely depend on the form in which the gem is submitted for identification. ZGTL classifies the gems and minerals on the basis of group/species/variety where applicable, based on the nomenclature guidelines drawn by the CIBJO, the World Jewellery Confederation
For grading reports all diamonds are graded for 4 C (cut, clarity, colour and carat weight) quality grading as per well-established international criteria.
