Nonetheless, gem labs use these colour terms on their reports to fulfil the demand from the trade. Since there is no definite agreement as to precise colours and quality criteria a stone has to fulfil, there is little consistency on how these trade colour terms are applied within the industry. They tend to blend colour attributes with other quality characteristics and rarity.

Such terms - often reflecting regional preferences – are typically assigned to gemstones of superior quality. Historically, the gem trade uses dedicated terms to describe specific colours and qualities of gemstones. However, not all labs are equally strict in the application of agreed definitions, limiting the result of these harmonisation efforts. The Gübelin Gem Lab does pursue harmonisation, specifically for trade colour terms. There is a global consensus that harmonisation would be the right thing to do, but it does not happen. Debates about such inconsistencies typically relate to country of origin, but also to treatment status and colours, namely trade colours such as pigeonblood red or royal blue. Indeed, conflicting results pose a challenge to a seller, and might raise doubt in the stone and the seller alike. Differences in reports from different gem testing laboratories, and hence efforts to harmonise the work of labs, are notorious in our industry.

Royal blue sapphire