Turquoise: A Comprehensive Guide

Authentic Persian turquoise jewelry

Introduction

Turquoise, known as “綠松石” (Lǜ sōng shí) in Chinese, is a captivating gemstone with a rich history. Despite its English name suggesting Turkish origins, turquoise was not mined in Turkey but likely gained its name because it was traded through Turkish markets to Europe. In China, turquoise has been treasured since ancient times, with artifacts dating back to the Peiligang Culture (7,000–5,000 BCE) and the Yangshao Culture (5,000–3,000 BCE). Historical texts, such as the Qing Hui Dian Tu Kao (清會典圖考), document its use in imperial rituals and adornments.

Physical and Chemical Properties

Turquoise is a hydrous phosphate mineral composed of copper and aluminum, with the chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O. Key characteristics include:

Hardness: 5–6 on the Mohs scale (varies by type).
Density: 2.6–2.9 g/cm³.
Luster: Waxy to subvitreous.
Transparency: Opaque, with microscopic crystalline structures visible under high magnification.
Color: Ranges from sky blue to greenish-blue, often with brown or black veining (iron oxide impurities).

Color, Texture, and Grading

Turquoise is classified by color, hardness, and purity:

Porcelain-Grade (瓷松):

Color: Vibrant sky blue.
Hardness: 5–6 (highest quality).
Features: No visible veins, glass-like finish.
Subtype: “Persian Spiderweb” turquoise, with delicate dark veining, is highly prized.

American-Grade:

Color: Pale blue or green.
Hardness: 4–5.
Features: Less vivid, may have faint veining.

Egyptian-Grade:

Color: Blue-green with uneven patches.
Hardness: 3–4.
Features: Porous texture.

Afghan-Grade:

Color: Dull yellow-green.
Hardness: Below 3.
Features: Heavy veining; low gemstone value.

Global Sources

Turquoise forms in copper-rich, weathered rock zones. Major deposits are found in:

Iran: Source of the finest “Persian blue” turquoise.
USA: Arizona and Nevada produce high-quality stones.
China: Hubei Province is the primary source, with secondary deposits in Shaanxi, Xinjiang, and Qinghai.

Cultural and Artistic Significance

Turquoise has been used for millennia in:

Jewelry: Beads, rings, and inlays.
Art: Carvings of figures, flora, and fauna.
Rituals: Imperial offerings and ceremonial objects.

The gem’s most valued form is pure sky-blue “瓷松,” often set in silver or gold for contemporary designs.

Why Turquoise?

Historical: A bridge between ancient traditions and modern fashion.
Aesthetic: Its unique blue-green hues complement both warm and cool tones.
Spiritual: Revered in many cultures for protection and healing.

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Turquoise: A Comprehensive Guide