Current Edition
About the 2026 Turquoise Standard
The 2026 edition establishes the current methodology for official grading of natural turquoise cabochons by relative rarity of natural formation.
What the Current Edition Covers
The current edition applies exclusively to natural turquoise shaped and polished as a cabochon. The official grade applies to the finished face of the cabochon, including the domed, convex, or flat top and beveled sides. The bottom is not included in the official grade.
What the Standard Is For
Rarity of Natural Formation
The Standard evaluates turquoise as a gemstone whose grade reflects the rarity of its natural formation.
Consistent Methodology
It provides a consistent and repeatable methodology for interpreting and communicating rarity through standardized comparison to Master Stones.
Defined Boundaries
It does not evaluate beauty, artistic preference, market value, provenance, or mineralogical classification except where specifically addressed.
How the Four-Year Review Fits In
The peer review history remains part of the Standard’s development record. From proposal through testing, revision, and the 57-stone study set, the review period helped move the project from an idea about turquoise quality into the current edition’s narrower, more repeatable grading framework.