Turquoise Grading Systems

By Joe Dan Lowry | ©December 16, 2019

Turquoise is one of the world’s most rare and colorful gemstones. For generations, many people in the gemstone world associations have continued to diminish turquoise’s monetary value and gemstone status by negatively comparing turquoise’s rare inconsistencies of colors, intrusions of other minerals, and its medium hardness to other gemstones such as a diamond. Turquoise is a rare and distinctive gemstone because of these so-called inconsistencies. The specific geological area and available mineralogy are what determine the unique size, density, hardness, color and intrusions of a turquoise. As each of these diversities in color, intrusions, and source are identified and cataloged by picture, the rarest of these categories have become the most collectible turquoise.

The concept of grading turquoise slowly developed with each culture and civilization that mined and used it in their art and beliefs. Regional and cultural traditions developed into larger trade routes for the gemstone. Trade, culture, fashion trends, supply and opinions have continued to influence various turquoise markets around the world. The interaction and opinions shared between suppliers and buyers of turquoise has made the study of this gem entertaining and sometimes a little frustrating as miners, salespeople, artists and collectors buy, sell and market what they consider the best turquoise. 

Unlike other gemstones, turquoise does not have a single grading system. The most well-known tradition used to grade turquoise is the Persian Method, which defines the best grade as a stone with perfect clarity and the deepest blue color. The American Method, defines the best grade of turquoise as one from one of the most famous and rare mine sources, with the deepest blue color and spider web matrix.  As the trade of turquoise has developed into a global market, these two methods along with other regional traditions of grading turquoise have competed for acceptance on the world stage. By combining the Persian and American methods, a turquoise collector can define and grade the rarity of most turquoise.