The lapis lazuli deposits at Sar-e-Sang in Badakhshan, Afghanistan, have provided the raw material for objects fashioned of this stone since the earliest civilizations. The mine, which lies in the Hindu Kush mountains, is difficult to reach and, because of climatic conditions, is opened only a few months during the summer. The lapis is found in veins in which calcite and dolomite are intimately associated with silicates such as diopside, scapolite, and forsterite. Pyrite is always present; the pure blue mineral is lazurite. The color of the lapis lazuli varies according to the amount of the various impurities contained therein. Well-formed crystals of lazurite with the dominant (110) shape are rarely found. This article examines the crystallographic properties of lapis lazuli, the site of Sar-e-Sang and the lapis lazuli deposits there, and offers an explanation for the genesis of the material. -- AATA