Turquoise Gemstones – Properties, Origins, Treatments and Buying Guide

Turquoise is one of the most iconic gemstones, known for its vibrant blue to green colours and unique veining patterns. It has been valued by cultures worldwide for thousands of years as a symbol of protection and prosperity.

In this guide we examine turquoise from a professional gemmological and commercial perspective, covering its physical properties, crystal structure, treatments, origins, and how to identify fine-quality stones.

Turquoise is a hydrated phosphate of copper and aluminium (CuAl₆(PO₄)₄(OH)₈·4H₂O) that forms in arid, copper-rich regions as nodules or vein deposits. Its vivid sky-blue to green colours are caused by varying copper and iron content. High-quality turquoise is prized for its uniform colour and fine matrix patterns, making it highly collectible and suitable for jewellery.

Turquoise has the chemical formula:

CuAl₆(PO₄)₄(OH)₈·4H₂O

It is composed primarily of:

Copper (Cu) – gives blue colour
Aluminium (Al)
Phosphate (PO₄)
Water (H₂O)

Minor iron or zinc content may shift the colour toward green. The pattern of brown or black veining (matrix) comes from host rock inclusions.

Turquoise belongs to the phosphate mineral family.

Its crystal system is triclinic, though gem-quality material is usually massive or nodular rather than forming distinct crystals.

Turquoise is valued for its opaque to semi-translucent appearance, vibrant colours, and unique matrix patterns, giving each stone a distinctive character for jewellery and collection.

Lustre
Waxy to sub-vitreous, giving soft shine.

Transparency
Typically opaque; some high-quality nodules are semi-translucent at edges.

Refractive index
1.61 – 1.65, providing subtle internal reflection.

Specific gravity
2.6 – 2.9, typical for phosphate minerals.

Turquoise occurs in shades of:

Sky blue
Robin’s egg blue
Green-blue
Yellowish-green
Matrixed varieties (brown, black, or grey veining)

Uniform, bright blue material with minimal matrix is most valued

Turquoise has a Mohs hardness of 5–6, making it relatively soft. It is suitable for earrings, pendants, and inlay work, but caution is needed for rings and bracelets to avoid scratching.

Many turquoise stones are stabilised with resin or wax to improve durability and polish. Rarely, dyed turquoise is used to enhance colour. Natural, untreated stones remain the most collectible.

Avoid ultrasonic cleaners, acids, and harsh chemicals.
Use warm water, mild soap, and a soft brush.
Store separately from harder gemstones to prevent scratches.

Major sources of turquoise include:

Iran (Persian turquoise)
USA (Arizona, Nevada, New Mexico)
China
Egypt
Mexico