Turquoise Quality Factors

Different colours of turquoise.
The green turquoise cabochon, from an American mine, might become part of a designer’s unique jewellery piece. The even blue colour of the cabochon on the right would be called “Persian blue” in the trade. Photo: Robert Weldon/GIA, Dr Eduard J. Gübelin collection

Fine-quality turquoise is sought after around the world by designers of unusual jewellery pieces.

Typically, turquoise is judged on three basic quality factors—colour, texture, and the presence or absence of matrix.

Turquoise Colour

Blue Turquoise
The most-prized turquoise colour is an even, intense, medium blue, sometimes referred to as robin’s egg blue or sky blue in the trade. The traditional source for this colour is the Nishapur district of Iran, so you’ll also hear it described as “Persian blue”, whether or not it was actually mined in Iran.

Green Turquoise
Generally speaking, turquoise with a green to greenish blue colour is less desirable than turquoise with a pure blue hue, but it depends on personal preference. There are some contemporary designers who actively seek avocado and lime green turquoise.

Turquoise Brooch and Graduated Bead Strands
The turquoise in the brooch and graduated bead strands is from Arizona’s Sleeping Beauty Mine. Its smooth, even colour represents the appearance prized by most collectors. - Photo: Valerie Power/GIA. Courtesy: GLEAM
- Courtesy GLEAM

Turquoise Pattern

Turquoise can be semi-translucent to opaque, with a colour that usually ranges from light to medium blue or greenish blue. It’s often mottled and sometimes has dark splotches. It might also have veins of matrix running through it (matrix is a remnant of its surrounding rock). The material known as spiderweb turquoise contains fine seams of matrix that form attractive web-like patterns.

Freeform turquoise cabochons
These free-form turquoise cabochons show a typical matrix pattern. Photo: GIA

The most valuable turquoise is an even medium blue, with no matrix and the ability to take a good polish.

Turquoise Cut

Turquoise is most often cut as a cabochon. The smoothly rounded dome shape sets off turquoise’s colour, texture and any matrix beautifully. In addition, manufacturers and artisans fashion turquoise into round or oblong beads for strand necklaces, and into small, flat pieces that are popular in jewellery inlays. Some top-colour blue turquoise is engraved with Persian or Arabic inscriptions, inlaid with gold. Lower-quality rough material might be tumbled into “nuggets".

“Pegged Nugget” turquoise bracelet
This stylish and unusual “Pegged Nugget” bracelet contains about 100 flat turquoise nuggets that are attached with flat silver pegs. -– Photo: Maha Tannous/GIA. Gift of Robert Lee Morris
Intarsia box
This intarsia box created by Nicolai Medvedev includes flat pieces of turquoise as part of its inlaid design. -– Photo © GIA & Tino Hammid, gift of Carol and Fred Seeman

Turquoise Carat Weight

Turquoise is weighed in carats, and five carats equal one gram. Turquoise is available in a wide range of sizes. All sizes, even very small stones, are used in Native American jewellery, and large pieces of turquoise rough are popular for carvings. For any size, the quality and evenness of the colour is the overriding value factor.

Turquoise Rough and Gem Pieces
A single large piece of rough can yield several much smaller pieces of fine, evenly coloured turquoise. A gem cutter has to work around the host rock to avoid ending up with a much less valuable gem. Photo: GIA, Dr Eduard J. Gübelin collection.