Lapis Lazuli (青金石)

Basic Information

• Etymology: The English name “Lapis Lazuli” derives from Latin lapis (meaning stone) and Persian lāžaward (the name of a historic region in Afghanistan, modern-day Badakhshan, famous for lapis lazuli, meaning blue). It’s also known as azure stone in English craft circles; ancient Chinese names include Jinbi, Diandai, or Biluli.
• Chemical Composition: Formula is (Na,Ca)₈(AlSiO₄)₆(SO₄,S,Cl)₁₋₂, a member of the sodalite group in framework silicate minerals.
• Crystal Characteristics: Isometric crystal system, crystal form is dodecahedron; aggregates are dense massive or granular structures.

Physical Properties

• Color: Deep blue, violet blue, sky blue, greenish blue, etc. White streaks appear with abundant calcite; golden yellow specks on blue background with pyrite.
• Luster: Vitreous luster.
• Transparency: Translucent to opaque.
• Hardness: 5–5.5 on the Mohs scale.
• Relative Density: 2.38–2.45.
• Cleavage & Fracture: Imperfect {110} cleavage; uneven fracture.

Grades Classification

1. Top-grade Lapis Lazuli: Lapis lazuli mineral content >99%, no pyrite, pure, tough and fine texture, intense and uniform deep blue.
2. High-grade Lapis: Mineral content 90%–95%, no white veins, sparse stippled pyrite and minor impurities, pure, dense texture with uniform color.
3. Jingelang (Low-grade): Low mineral content, dense pyrite, significant white calcite streaks/spots, pale and uneven blue.
4. Cuishengshi (Lowest grade): Minimal lapis lazuli mineral, generally no pyrite, high calcite content, only scattered blue dots or mixed blue-white mottling.

Formation & Major Origins

• Formation: A metamorphic rock formed by contact metasomatism, mainly occurring in silicate-magnesium skarn and calcareous skarn.
• Origins: Afghanistan (the most historic and premium source), Russia, Chile, Canada, etc. Afghanistan’s Badakhshan is renowned for the world’s finest lapis lazuli for thousands of years.

Historical & Cultural Significance

• As early as the 6th millennium BC, Afghan lapis lazuli was transported to Mesopotamia, Egypt and Greece via the Lapis Lazuli Route—one of the world’s earliest trade routes.
• In ancient India and Iran, it was a precious gem alongside turquoise and coral; in ancient Greece and Rome, wearing lapis lazuli was a symbol of wealth and status.
• It is one of the Seven Treasures of Buddhism in ancient China. Valued by emperors for its “sky-like blue hue”, it was used for the imperial court beads in the Qing Dynasty to worship the heaven (the highest ritual in ancient China).

Main Uses

• Ornamental & Jewelry: Carved artworks (statues, prayer beads, cylinder seals), and jewelry (necklaces, bracelets, earrings, rings) due to its vivid blue color.
• Pigment: Ground into a fine powder, it becomes ultramarine—a prized natural blue pigment. Widely used in Renaissance oil paintings and murals (e.g., the Mogao Grottoes in Dunhuang, China), famous for its brilliant and fade-resistant hue.