Turquoise Buying Guide: Quality, Treatments, and Origin

Introduction

Turquoise has been treasured for thousands of years, from ancient Egyptian pharaohs to modern jewelry enthusiasts. Its captivating blue-to-green hues and distinctive matrix patterns make it one of the most recognizable gemstones in the world. However, the turquoise market is complex, with a wide range of qualities, treatments, and imitations. This comprehensive guide will help you understand what to look for when buying turquoise, how to assess its quality, and how to distinguish natural stones from treated and synthetic materials.

What Is Turquoise?

Turquoise is a hydrous phosphate of copper and aluminum, with the chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O. It is a secondary mineral that forms in arid regions through the weathering of rocks rich in copper, aluminum, and phosphorus. Turquoise is cryptocrystalline, meaning its crystals are microscopic, and it typically occurs as nodules, veins, or masses. Its color ranges from sky blue to bluish green to green, influenced by the ratio of copper (blue) to iron (green) and other trace elements.

Physical Properties

• Mohs hardness: 5 to 6, which means it is relatively soft and can be scratched by harder materials.
• Specific gravity: Approximately 2.6 to 2.8, varying with composition.
• Refractive index: About 1.61 to 1.65, though measuring it on opaque stones is often difficult.
• Crystal system: Triclinic (though rarely seen in crystal form).

Because turquoise is porous and relatively soft, it is almost always treated to enhance durability and color. Understanding these treatments is essential for any buyer.

Evaluating Turquoise Quality

When assessing turquoise, gemologists and buyers consider four main factors: color, matrix, texture, and treatment.

Color

The ideal turquoise color is a pure, even, medium to dark sky blue. This hue is often described as "robin's egg blue" or "Persian blue," though top-quality stones from various origins can achieve this color. Green shades are generally less valued unless they have a pleasing, even tone. Color should be uniform across the stone, with no pale or chalky areas.

Matrix

Matrix refers to the host rock or veining within turquoise. It can be black, brown, gray, gold, or even red, depending on the minerals present. Some buyers prefer a clean, matrix-free stone, while others appreciate a fine spiderweb pattern. The quality of the matrix depends on its aesthetics, contrast, and evenness. A well-defined, harmonious matrix can increase value, especially in American turquoise where distinctive patterns are prized.

Texture and Finish

High-quality turquoise is hard, dense, and takes a good polish. It should feel smooth and waxy, not chalky or porous. A well-polished stone will have a subtle luster. In contrast, poor-quality turquoise may be soft, porous, and appear dull after polishing.

Treatment Status

The most critical factor in turquoise valuation is whether it has been treated. Natural, untreated turquoise is rare and commands a premium. Many stones are stabilized, coated, dyed, or otherwise enhanced to improve color and durability. The treatment should always be disclosed by reputable sellers.

Common Treatments and Enhancements

Most turquoise on the market today is treated. Understanding these processes helps you know what you are buying and how to care for it.

Stabilization

Stabilization involves impregnating porous turquoise with a clear resin or plastic to harden it and improve its color. This process is often used on stones that are too soft to cut or polish naturally. Stabilized turquoise is more durable and resists scratching and fading, but some purists consider it less desirable than natural turquoise. It is the most common treatment in the industry.

Oil or Wax Impregnation

Historically, turquoise was often treated with oils, waxes, or paraffin to enhance color and luster. These treatments are less permanent and can wear off over time, especially with exposure to heat or solvents. Oiled or waxed turquoise may show a temporary improvement that diminishes with wear.

Dyeing

Pale or chalky turquoise may be dyed to deepen or alter its color. Dying is generally considered a less desirable treatment because it can be superficial and may fade or bleed. The use of dye is not always obvious, so a laboratory test may be needed to detect it.

Reconstituted Turquoise

Reconstituted turquoise is made by crushing low-quality turquoise and mixing it with resin, then pressing it into blocks. This material is often cut into beads or cabochons and can resemble natural turquoise, but it lacks the natural structure and often has a more uniform appearance. It is a type of composite or treated material, not natural turquoise.

Other Treatments

Some turquoise is coated with a plastic or epoxy to create a smooth surface, and occasionally stones are dyed to imitate more valuable varieties. Advanced treatments may be difficult to detect without laboratory analysis.

Synthetics and Imitations

In addition to treatments, buyers should be aware of synthetic turquoise and gemstones that imitate turquoise.

Synthetic Turquoise

Synthetic turquoise has the same chemical composition and crystal structure as natural turquoise but is created in a laboratory. The first commercially successful synthetic turquoise was produced in the 1970s by Pierre Gilson, and it remains a common type. Gilson turquoise is often homogeneous and may have a distinctive appearance, but it can fool the untrained eye. Laboratories can identify synthetic turquoise by its microscopically uniform texture and the absence of natural inclusions.

Imitation Materials

Several natural and artificial materials are used to imitate turquoise, including:

• Howlite: A white mineral with gray veining that is often dyed blue to resemble turquoise.
• Magnesite: Another white mineral that is dyed and veined to imitate turquoise.
• Plastic or ceramic: These can be molded to mimic turquoise's appearance.
• Dyed chalcedony: Some quartz varieties are dyed blue-green and sold as turquoise.

These imitations can sometimes be identified by their heft (plastic imitations are lighter), and by a close examination of the veining and color distribution.

Geographic Origins and Their Influence on Value

While turquoise is found worldwide, certain localities have gained renown for their distinctive colors and quality. However, origin alone does not determine value; a combination of color, matrix, and treatment is what ultimately matters.

Iran (Persia)

The famous Persian turquoise, particularly from the Nishapur mines in Iran, is renowned for its pure sky-blue color and minimal matrix. Persian turquoise has been historically prized and often used in fine jewelry. The name "turquoise" itself derives from the French for "Turkish," as the stone came to Europe through Turkey.

Southwestern United States

Turquoise from Arizona, New Mexico, Colorado, and Nevada is highly collectible, often featuring dramatic matrix patterns and varied colors. Mines such as Sleeping Beauty (Arizona), Kingman (Arizona), and Bisbee (Arizona) are famous for specific appearances. Sleeping Beauty turquoise is known for its uniform sky-blue color with no matrix, while Bisbee turquoise often shows a beautiful blue with a smoky black matrix. Many American turquoise deposits are now depleted, making certain old stocks valuable.

China

China is currently a major producer of turquoise, particularly from Hubei Province. Chinese turquoise can range from blue to green and is often stabilized or treated before entering the market. It is commonly used in beads and carvings.

Other Sources

Turquoise is also mined in Egypt (the historic Sinai Peninsula deposits), Tibet, Mexico (for its distinctive green stones), and many other countries. Each source may have typical characteristics, but they cannot be reliably identified by appearance alone. Only advanced laboratory testing can sometimes determine geographical origin, and even then, it is not always conclusive.

How to Identify Untreated vs. Treated Turquoise

Distinguishing natural turquoise from treated or synthetic materials can be challenging, even for experienced gemologists. Here are some clues and limitations:

• Price: Natural, untreated turquoise is rare and expensive. If the price seems too good to be true, it likely is.
• Consistency: Perfectly uniform color and matrix may indicate reconstituted or synthetic material, but some natural stones are also uniform.
• Hot needle test: A hot needle applied to a hidden area may cause resin or plastic to melt and emit a smell. This should be done with extreme caution as it can damage the stone and is not always conclusive.
• Chemical tests: Dropping a solvent like acetone on a questionable area can reveal dye if it bleeds, but this is also risky and can damage the stone.

For a reliable determination, a gemological laboratory can use advanced techniques such as infrared spectroscopy, X-ray diffraction, and scanning electron microscopy to identify treatments and imitations. For high-value purchases, a laboratory report from a reputable lab is worth the investment.

Turquoise in Jewelry and Care

Turquoise has been used in jewelry for millennia, from ancient amulets to Native American silverwork. Its color and texture offer versatility, but its softness and porosity require special care.

Durability and Setting

In addition to its Mohs hardness of 5-6, turquoise's toughness is generally good, but it is susceptible to chipping and scratching. It is also sensitive to chemicals, heat, and prolonged sunlight, which can cause color changes. Stabilized turquoise is more resilient to these factors than untreated stones.

In jewelry, turquoise is often set in bezels or protected by surrounding metal to shield it from impact. Rings are risky because they are subjected to knocks, but many turquoise rings are worn with proper care. Earrings and pendants are safer choices.

Cleaning and Maintenance

Clean turquoise with a soft, damp cloth and mild soap, if necessary. Do not use ultrasonic or steam cleaners, as they can damage the stone and any treatments. Turquoise should be stored separately from harder gemstones to prevent scratches, and it should be kept away from perfumes, cosmetics, and household chemicals. Untreated turquoise is especially sensitive and can absorb oils and liquids, altering its color.

The History and Cultural Significance of Turquoise

Turquoise has a rich history and cultural heritage.

Ancient Uses

The ancient Egyptians mined turquoise in the Sinai Peninsula, using it in jewelry and burial masks. The Aztecs and other Mesoamerican cultures treasured turquoise for its sky-blue color, using it in mosaics and ceremonial objects. In Persia, turquoise was the national gem, and it is said that the purpose of the stone was to protect the wearer from evil.

Native American Traditions

In the American Southwest, turquoise holds deep cultural significance for many Native American tribes. It has been used in jewelry, amulets, and ceremonial items for centuries. The Navajo, Zuni, and Hopi peoples are famous for their turquoise jewelry, incorporating it into silverwork and beadwork. Turquoise is considered a symbol of friendship, protection, and good fortune.

Trade and the Name

Turquoise appeared in Europe through Turkish traders, leading to the name "turquoise," meaning "Turkish stone" in French. It became popular in 17th-century European jewelry, often symbolizing wealth and prestige.

Metaphysical and Spiritual Properties

Turquoise has long been associated with metaphysical beliefs and healing practices, though these are not scientifically proven. In many cultures, turquoise is believed to:

• Promote emotional balance and calm – thought to alleviate anxiety and stress.
• Enhance communication and self-expression – believed to align the throat chakra.
• Provide protection – historically worn as an amulet to ward off evil spirits or harm.
• Connect with the sky and higher consciousness – associated with spiritual attunement and intuition.

Some also associate turquoise with the zodiac signs of Sagittarius and Pisces, and with the traditional birthstone for December (though modern lists vary). These beliefs are part of cultural and spiritual traditions rather than verified scientific effects.

Buying Turquoise: Practical Tips

When purchasing turquoise, consider the following advice:

• Always ask about treatments. Reputable dealers will disclose whether the turquoise is natural, stabilized, dyed, or reconstituted.
• Request a receipt or certificate. For expensive pieces, a laboratory report can confirm authenticity and treatment status.
• Inspect the color and matrix personally. Look for evenness, and be aware that some inconsistencies are natural.
• Compare prices. If one seller offers a stone that looks similar to another at a significantly lower price, be suspicious.
• Consider the intended use. For everyday rings, a stabilized stone may be more practical than an untreated one, which is more fragile and valuable.

Conclusion

Turquoise is a gemstone of unique beauty and cultural heritage, but buying it requires knowledge and caution. The most important factors are color, matrix, and treatment status. Natural, untreated turquoise is the rarest and most valuable, but most turquoise on the market is stabilized to improve durability. Understanding the differences between natural, treated, synthetic, and imitation materials will help you make an informed purchase. Always seek transparent disclosure from sellers, and for significant investments, consider professional gemological analysis. With proper care, turquoise jewelry can be enjoyed for generations, carrying both the aesthetic appeal of a classic gemstone and the cultural richness of its long history.