Coloured Gemstones

Coloured gemstones come in an incredible array of colours and varieties. Emeralds, rubies and sapphires are most well-known, but our testing services and research efforts go far beyond these three varieties. Our expertise in treatment detection and origin determination of coloured gemstones is based on decades of research, a large reference collection and continuously developing new techniques to analyse these treasures of nature.



Complete 4Cs –carat, clarity, colour, cut- grading of natural diamonds can be carried out by GRC. The diamonds must be loose and cannot be graded in a mounted state. GRC does not offer grading reports for synthetic diamonds.



Natural pearls are some of the oldest gems collected by mankind. Natural pearls continue today to be desired objects at auction. GRC has tested many of the world’s most iconic natural pearls in recent years. Our expertise in pearl testing rests on continuous research and expeditions to natural pearl sources and cultured pearl farms worldwide.



Jade is a polycristalline aggregate made of fine and very densely interwoven mineral grains or fibres, which give it its outstanding workable properties. Based on historic references, the Chinese understanding of the term jade is not equal to the Western understanding of the term, which has been defined (CIBJO) to consist either of jadeite (mineral of the pyroxene group) or nephrite, an intermediate member of the solid solution series between actinolite and tremolite (amphiboles). In the Chinese understanding, the term jade was historically separated into the terms Ying Yù (hard jade), mostly corresponding to pyroxenitic jade (also known as “Fei Cui” 翡翠) and Ruan Yù (soft jade), which apart from nephrite also includes minerals of the serpentine group (Xiù Yù jade, Liaoning). As a gemmological laboratory with a scientific approach, we strictly use mineralogical and chemical parameters to identify jade, either as jadeite-jade or nephrite-jade and to disclose any treatments applied on these stones.



Preferrably, gemstones should be submitted to GRC for testing in a loose unmounted state. Coloured gemstones set in jewellery can generally be tested as far the mounting permits it.