Azure sky, robin’s egg blue: Vivid shades of turquoise define the colour that’s named after this gem.

Turquoise is a unique gemstone found in only a few select regions of the world. It forms in dry, arid areas where acidic, copper-rich groundwater interacts with minerals containing phosphorus and aluminium. This chemical reaction creates a porous, semi-translucent to opaque compound of hydrated copper and aluminium phosphate.

Although turquoise lacks the sparkle and clarity of transparent gemstones like ruby, emerald, and sapphire, its rich history and vibrant colour make it highly desirable. Its hues range from dull green to grass green to bright, sky blue. Turquoise is cherished for its ancient significance and captivating shades.

The most coveted turquoise colour, often referred to as “Persian blue” or “robin’s-egg blue,” traditionally comes from the Nishapur district in Iran, formerly known as Persia. This shade remains highly prized, regardless of the actual source of the turquoise.

Top-quality turquoise is often cut into cabochons, but it can also be fashioned into beads or flat pieces for inlays. Designers have long been inspired by turquoise for its use in elegant jewelry, from contemporary pieces to traditional Native American designs crafted by the Pueblo, Hopi, Zuni, and Navajo peoples. These pieces are frequently collected for their distinctive style and cultural significance.

Turquoise's softness makes it ideal for carving, and it is used by artists across Europe, Asia, the Middle East, and the Americas for both jewellery and art objects. It is commonly carved into talismans with symbolic meanings, such as animal figures known as fetishes.

The texture of turquoise is determined by its structure and composition. It consists of microscopic crystals that form a solid mass. When these crystals are densely packed, the turquoise has a finer texture and a waxy lustre when polished. Conversely, turquoise with a more porous structure has a coarser texture and a duller appearance.

Turquoise is relatively soft, scoring 5 to 6 on the Mohs scale, and its durability varies with texture. Coarse-textured turquoise may be less durable, while fine-textured turquoise offers better toughness.

Turquoise often contains natural markings, known as matrix, from the host rock. These can appear as dark brown or tan veins and splotches. A specific type known as "spiderweb turquoise" features delicate, web-like patterns of matrix that provide a striking contrast to the bright blue of the gemstone.

In the market, turquoise with no matrix commands the highest prices, while stones with attractive spiderweb matrix are also highly valued.