21/05/2022
Afghan Tourmaline
In recent decades Afghanistan has become famous for its tourmalines–and with good reason, as spectacular finds of gem tourmaline have been repeatedly made in the country. Some of the most desirable tourmalines are the blue-green shades, and also a deep rich green tinted with blue. The color can shift slightly with the lighting, appearing a brighter under fluorescent lights and a deeper blue-green in daylight. The rarest and most expensive tourmaline is the paraiba variety - a neon-like blue or green that is colored by traces of copper. Afghanistan is quite capable of producing some of the world's finest, most intensely colored Tourmalines. Though these are often over shadowing by cuprian stones from Mozambique, the bright sea-green colors of these Afghani stones is quite unique. At their best, green tourmalines are transparent, brilliant, and clean, with attractive bluish green hues. Most green tourmalines are strongly pleochroic. Stones that show attractive colors in both directions—such as bright green in one and blue in another—are the most valuable. Literally hundreds of thousands of carats of good, gem-quality tourmaline and fine kunzite have emerged from the Kolum district of the Nuristan region northeast of Kabul since active mining began there in the early 1970s. This area is also known for its production of fine aquamarine. From the Kabul-Jalalabad Road go due north to Mehtar Lam approximately 20 km and then 40 km northeast to the village of Nuristan. The passable road ends several kilometers past Nuristan, and all further travel to the mines must be by foot. The rocks of this area are quite varied, and include metamorphic (gneisses, schists, quartzites, and migmatites) and igneous (gabbros, diorites, and granites) rock types. Gem-bearing pegmatites in Nuristan were first studied in the early 1970s by Soviet geologists (Rossovskiy et al., 1976, Rossovskiy et al., 1978; Rossovskiy, 1981).A number of separate pegmatite localities are known, but the most important gem producers seem to be those north of the village of Nuristan at Nilaw, Suraj, Mawi, and Korgal.
The pegmatites vary greatly in size and shape-in veins or lenses up to 40 m thick and up to several kilometers long. The pegmatites range from simple unzoned bodies to those that have complex internal zonation, but the latter group appear to be the more important gem sources. Major minerals include quartz, albite, microcline, schorl tourmaline, muscovite, and lepidolite, along with various minor phases. Crystals of gem tourmaline, spodumene, and beryl occur in cavities up to 50 cm across that are distributed along the central portion of the pegmatite. These crystals are quite remarkable in terms of their size, crystal perfection, and diversity of color. For ex- ample, Rossovskiy (1981) describes tabular, gemmy crystals of spodumene up to 45 cm long and “pencil” crystals of gem tourmaline up to 20 cm, both in a wide variety of colors.
For the most part, the crystals are found in soft, powdered clay that fills pockets within quartz-rich zones in the pegmatite. While the kunzite and tourmaline crystals usually occur in close proximity (within a few meters) of each other, only occasionally are the two gem minerals found in the same pocket. Because both are, for the most part, founding situ in the primary pegmatite, the crystals are usually well formed and complete.
Approximately 500 miners work the Nuristan region on a daily basis. To pe*****te the hard pegmatite, they commonly use large drills. The gem-bearing areas of the pegmatite are usually en- countered between 11 and 20 m below the surface. When they reach a pegmatite pocket, the miners remove the gem crystals by hand, using only a few small tools to scrape away the encasing clay. As with the emerald mines in Panjshir, the Nuristan miners usually work year-round, in spite of the severe weather conditions that commonly plague the area.
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