How Turquoise Is Graded: Color, Clarity, and the Persian vs. American Systems
Two competing grading standards define fine turquoise: the Persian system prizes perfect clarity and deepest blue, while the American system prizes named-mine origin paired with good blue color and spiderweb matrix. Price ranges from seven cents to $1,000 per carat depending on which standard applies and how rare the source.
Mateo's Field Notes
The difference between the two systems is not purely aesthetic — it reflects two different histories of how turquoise entered the gem trade. Lowry states the contrast plainly: "The Persian system… defines the best grade as a stone with perfect clarity and the deepest blue color." (~line 9222–9226.) Against that: "The American system defines the best grade as a stone that is from one of the most famous and rare mines that has a good blue color and a spiderweb matrix." (~line 9218–9340.) Under the American system, provenance is inseparable from quality.
Color depth is not merely a preference in either system. "The darkest colors are the rarest to find and therefore have a greater value than lighter colors." (Lowry, ~line 9310.) The mines that produce the darkest, hardest material are themselves rare: "Turquoise from such mines as Number Eight, Bisbee, Lander Blue, Lone Mountain, the best Persian turquoise…" (Lowry, ~line 9340) — Lowry cites these as world benchmarks.
The historical price record from the Great American Turquoise Rush provides a useful anchor. Chambless documents that the best American material was compared directly against Persian: "When The Great American Turquoise Rush began in 1890, one of the principle reasons for the desire to secure and produce turquoise from the Southwest was the similarity in quality compared with Persia." (~line 9657–9675.) At the peak of that rush, the finest material from certain districts — Chambless cites comparison with Courtland, Arizona and Cerrillos — was "considered, with Courtland, Arizona and Cerrillos, as the best in the world and brought up to $20 per carat wholesale." (~line 4480–4490.) That is a 1890s wholesale price; the modern ceiling Lowry documents is $1,000/carat retail for the finest cabochons (2007 data, ~line 9710), with most commercial material under $5/carat.
A 1905 trade catalog entry preserved by Chambless captures the moment American turquoise claimed parity with Persian: "A little lower in price than the Persian Turquoise and a little better in quality. In hardness, in durability, in color, the Toltec Turquoise are unequaled by any others in the world." (~line 10069–10075.) The boosterism is period-appropriate, but the hardness claim reflects a real distinction: American Southwest material from specific mines is demonstrably harder than much Persian rough.
Collector's Handbook
- Persian benchmark. Under the Persian system, look for: uniform sky-blue color, high clarity, no visible matrix, maximum color saturation. This is the standard for classic robin's-egg blue stones.
- American benchmark. Under the American system, look for: confirmed mine of origin (Number Eight, Bisbee, Lander Blue, Lone Mountain), good blue color, and an even spiderweb matrix. All three criteria together define top grade.
- Color is not subjective. Darker = rarer = more valuable in both systems. Pale, chalky, or greenish color signals lower grade or excessive iron content.
- Price reality check. Under $5/carat = commercial, likely treated. $5–$50/carat = mid-grade, may be natural. Above $50/carat = demand documentation of mine, treatment status, and ideally gemological report. Above $200/carat = named-mine gem-grade territory; insist on paper.
- Provenance chain. The American system requires knowing the mine. "Southwest turquoise" without a mine name cannot be graded under the American standard. If a seller cannot name the mine, price accordingly.
Related Entries in the Directory
Browse artists who source named-mine material in the Silversmith Directory. See also the Matrix Guide for how spiderweb patterns are classified.
Primary Sources
- Lowry, Joe Dan & Joe P. Lowry. Turquoise: The World Story of a Fascinating Gemstone. Gibbs Smith, 2010, ~line 9218–9226 (Persian and American systems); ~line 9310 (darkness = value); ~line 9340 (named mines benchmark); ~line 9710 (price range).
- Chambless, Philip & Mike Ryan II. Turquoise in America, Part One: The Great American Turquoise Rush 1890–1910. Callais Press, 2021, ~line 4480–4490 (wholesale peak price); ~line 9657–9675 (Rush origin, Persian comparison); ~line 10069–10075 (Toltec 1905 catalog entry).