Turquoise: The Complete Guide

Turquoise has been treasured continuously for longer than almost any other gem material. Egyptian pharaohs wore turquoise. Persian emperors used it to dome their palaces. Tibetan monks wore it as spiritual protection. Native American peoples of the Southwest created jewellery traditions with turquoise that have lasted thousands of years and continue to flourish. Today, turquoise enjoys a major market renaissance driven by bohemian fashion trends, celebrity endorsement, and renewed appreciation for natural stones with cultural depth. For jewellery professionals, turquoise is simultaneously one of the most commercially vibrant and most treatment-complex gems in the showcase.

What Turquoise Is

Turquoise is a hydrated copper aluminium phosphate mineral (CuAl6(PO4)4(OH)8 x 4H2O) that forms in arid regions through the weathering of aluminium-rich rocks in the presence of copper-bearing solutions. Its distinctive blue-to-green colour results from the copper content — higher copper produces more intense blue; iron substitution shifts the colour toward green. Turquoise forms in veins and nodules within host rock (matrix) and rarely forms large single crystals.

Turquoise has a Mohs hardness of 5-6, making it soft and porous. Its porosity creates both its characteristic surface texture and its vulnerability to staining, colour change from absorbed chemicals, and the commercial logic behind most treatments. Hard, dense, non-porous turquoise is considerably rarer than the porous material that forms the bulk of production.

Sources and Their Characteristics

Iran (Persia): The Classic Source

Iranian turquoise from the Nishapur mines in Khorasan Province is considered the world standard for finest colour — a pure robin’s-egg blue with no green modifier, produced by very low iron in the copper phosphate system. Natural (untreated), dense, non-porous Iranian turquoise is extremely rare and commands substantial premiums. The association between Iran and the finest turquoise goes back at least 2,000 years; Persian trade routes distributed this material throughout the ancient world.

American Southwest

The United States is home to some of the world’s most diverse and historically significant turquoise mines. The Sleeping Beauty mine in Arizona (closed to turquoise mining in 2012) produced a pure, even sky blue with no matrix that was among the most popular American turquoise for decades. Kingman (Arizona), Morenci (Arizona), Nevada mines (Carico Lake, Royston, Fox), and New Mexico mines (Cerrillos, Bisbee) each produce material with distinctive colour and matrix characteristics.

American turquoise is deeply embedded in Navajo, Zuni, Hopi, and other Native American jewellery traditions. Authentic Native American turquoise jewellery made by enrolled tribal members is a protected category under federal law (Indian Arts and Crafts Act). Professionals selling jewellery represented as Native American-made must exercise appropriate due diligence.

Other Sources

Tibet and China produce turquoise with characteristic greenish hues and often heavy matrix. Australian turquoise can be excellent quality. Mexico (Sonora, Zacatecas) produces good material. Egyptian turquoise from the Sinai Peninsula is historically significant though production is now minimal.

The Treatment Landscape

Treatment is perhaps more pervasive in turquoise than in any other gem category. Understanding the spectrum of treatments — and their commercial implications — is essential for any professional selling turquoise.

Natural (untreated): hard, dense, non-porous material that requires no stabilisation — rare and most valuable

Stabilised: low-grade porous material impregnated with clear resin to improve durability — widely accepted, must be disclosed

Enhanced: lightly stabilised with minimal resin, colour close to natural — intermediate category

Treated (dyed): colour artificially deepened or changed, often over stabilised base — must be disclosed, lower value

Block/pressed: powdered turquoise compressed with binding agent — disclosure required, significantly lower value

Simulants: howlite, magnesite, or plastic dyed turquoise blue — must be identified, not turquoise

Identifying Natural vs. Treated Turquoise

Natural, hard turquoise has a distinctive waxy lustre that differs from the slightly more plastic appearance of heavily stabilised material. A hot needle test (destructive, used only when appropriate) will cause resin to melt in stabilised material but not in natural stone. FTIR spectroscopy definitively identifies resins and other treatments. For the professional, laboratory testing of significant turquoise purchases is the only reliable approach.