corundum, Tajikistan.12, ruby, gems

Smith characterizes rubies and pink sapphires from marble-type deposits in the Turakuloma region of Tajikistan’s Pamir Mountains through examination of eight gemstones weighing 0.30–1.48 ct. Discovered in the early 1980s, these deposits had supplied only limited quantities to the international market. The best-known mine, Snejnaya, lies at approximately 3500 m, where severe weather restricts mining largely to June–August. The investigation combines standard gemological testing, immersion microscopy, identification of mineral inclusions by scanning electron microscopy with energy-dispersive analysis, optical and infrared spectroscopy, and semiquantitative X-ray fluorescence analysis. Samples are transparent, with saturated purplish-pink to purplish-red colours. Refractive indices of 1.761–1.762 and 1.770, birefringence of 0.008–0.009, specific gravity of 3.99–4.02 and uniaxial negative optic character are consistent with ruby and pink sapphire generally. Long-wave ultraviolet fluorescence is strong to very strong orange-red to red, while short-wave reactions are weaker. Internal growth structures indicate predominantly dipyramidal habits, with subordinate basal and rhombohedral faces; occasional colour zoning and rhombohedral twin lamellae are also recorded. Particularly useful microscopic features include columnar concentrations of short rutile needles and particles, highly resorbed calcite crystals arranged in roughly parallel rows, and small mineral or negative crystals accompanied by oriented equatorial thin films. Additional inclusions comprise titanite, zircon, rutile and plagioclase feldspar, together with healed fractures and negative crystals containing multiple fluid phases. Visible absorption is dominated by chromium, with broad bands near 405 and 550 nm and characteristic sharp lines. Infrared spectra show the expected corundum lattice absorptions but no detected mid-infrared features attributable to foreign minerals or structural hydroxyl groups. Analyses of five specimens identify chromium as the principal minor element responsible for colour, accompanied by titanium, vanadium, iron and gallium. Although the stones most closely resemble material from Quy Chau, Vietnam, their combined inclusion patterns appear distinctive and differ from features commonly encountered in several other ruby sources. Smith emphasizes the small sample population and the limited information available on production and reserves. At the time of writing, civil conflict, financial constraints and difficult access restricted exploitation, while fine faceted stones were generally 1.5 ct or smaller.