What Is Lapis Lazuli? Actually a Rock, Not a Mineral

Unlike most gemstones, which are a single mineral, lapis lazuli is technically a rock — an aggregate of several minerals fused together. The deep blue comes mainly from lazurite; white streaks are calcite; and the metallic gold flecks that fine lapis is known for are pyrite.

The best material — deep, even blue with minimal calcite and fine, well-distributed pyrite — has come from the Sar-e-Sang mines in Afghanistan for more than 6,000 years, making it one of the oldest continuously worked gem deposits on Earth. Lower-grade lapis, with heavier white calcite veining, is sometimes dyed to even out its color.