gems, spinel, Afghanistan, Tajikistan, balas ruby, Kuh-i-Lal, Pamir, geology

Kiselev examines the sequence of mineral formation in the magnesian skarns of the Kuh-i-Lal deposit in the southwestern Pamirs. The study distinguishes successive stages of skarn and post-skarn mineralization and relates changes in mineral assemblages to the evolving conditions of metamorphism and metasomatism. The principal skarn minerals include forsterite, enstatite, spinel and clinohumite, followed by later hydrous minerals produced during retrograde alteration. The work establishes a staged model for the formation and subsequent modification of the Kuh-i-Lal mineral assemblages, providing an important basis for later interpretations of the genesis of the deposit and its gem-quality spinel.