Appraisal of coloured gemstones
Unlike diamonds, there are no standardized value criteria for coloured gemstones. Each stone is unique, and its value depends on its quality, provenance and treatment. Mining is usually done by families and village communities who eventually trade them on the open markets. Experienced gemmologists and recognized laboratories often face difficulties establishing correct market values since they only cover the scientific part of the matter. Only those who are actively involved in the trade and who know the market situation are in a position to reliably estimate coloured gemstones.
Thanks to decades of experience in the trade, Frieden’s gemmologists, Thomas Frieden and René Lauper (G.G. GIA, SGG experts in gemstones), can determine the value of gems and their authenticity depending on their type, quality, origin and state of treatment. In particularly difficult appraisals, where the stone can only be analysed with instruments that cost millions, the stone is sent to the SEFF in Basel (Swiss Gemmological Institute). However, the SEFF only provides the scientific data – Frieden estimates the value.