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.
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.
Browse artists who source named-mine material in the Silversmith Directory. See also the Matrix Guide for how spiderweb patterns are classified.