gems, lapis lazuli, Afghanistan, species, locality, lazurite, geology, Badakhshan

The lapis lazuli from the Sar-e-Sang mine appears in veins within a thick marble bed embedded in a catazonal metamorphic series injected with pegmatites. The petrographic and mineralogical study concerns: the mineralized veins composed of massive or crystalline lazurite, associated with a number of other minerals, particularly feldspathoids; the silicate- and magnesium-rich veins without lazurite, also found within the marble; and finally the rocks of the surrounding metamorphic series: gneisses, pegmatites, and basic rocks. A comparison is made with the lazurite deposits of Prebaikalia (U.S.S.R.), which are very similar in their petrogenetic context. This comparison helps to propose a possible explanation for the genesis of the lazurite veins at Sar-e-Sang: they may have resulted from the complete transformation of pegmatites injected into the marble, through metasomatic interaction.