lazuli

Lazuli, commonly referred to as lapis lazuli, is a deep-blue metamorphic rock prized as a gemstone and historic pigment. The blue color is primarily due to the presence of the sulfur-containing mineral lazurite, a complex aluminum silicate. The rock also typically contains calcite and small amounts of other blue minerals such as sodalite, as well as pyrite crystals that can appear as golden flecks.

Etymology and sources: The name lazuli derives from Persian lazaward or lazhuward, meaning blue. The most famous ancient sources are the lapis mines of the Badakhshan region in northeast Afghanistan, which have supplied the material for thousands of years. Other deposits occur in locations such as Chile, Russia, and Myanmar, but Afghanistan remains the archetypal source in historical art and culture.

Uses and cultural significance: Lapis lazuli has been used for jewelry, carved figurines, inlay work, and ornamental objects since antiquity. Ground lazurite yielded ultramarine, the premier blue pigment in Western art until the development of synthetic ultramarine in the 19th century. The pigment’s name reflects its origin “beyond the sea.” In its solid form, lapis lazuli remains a popular gemstone for beads, cabochons, and intricate carvings.

Formation and geology: Lapis lazuli is not a single mineral but a rock formed through metamorphic processes where sulfur-rich fluids interact with calcium-rich rocks, producing lazurite crystals that impart the characteristic blue hue. Its appearance ranges from uniform blue to mottled patterns with white calcite and metallic pyrite.

Care and grading: Value is influenced by color intensity and uniformity, the amount of whitish calcite (which lowers value), and the visibility of pyrite inclusions. Its Mohs hardness is about 5–6, making it relatively softer than many gemstones.