| Deposit location: Nilaw (Laghman)
The stratiform pegmatite vein can be easily seen even from far away, forming white bands that show clearly in the abundant vegetation of the little narrow valley of Nilaw. In several places the pegmatites have been exploited with the use of dynamite.
Afghan law prohibits anyone from exploiting deposits of any kind whatever, excepting the employees of the Ministry of Mines, who work periodically on the most interesting zones. That prohibition even applies to the local village inhabitants; but this does not stop the smugglers who come, from Kabul and elsewhere, well prepared to make a fortune by selling the products of their work in the markets, especially in Kabul, Peshawar, Gilgit and even Tucson. The beryllium and lithium pegmatites of central Laghman are now prospected only for gems, and not for industrial elements such as Be, Li, Nb-Ta or Cs. In the Kunar field, beryllium is the only industrial element being exploited. The extent of the pegmatite veins of the zone called Kolum (Nilaw-Mawi) seems to be associated with the nature of the enclosure. In the Proterozoic formations they rarely reach 100 m in length and do not exceed 10 m in width, while in the gabbro-dioritic intrusions they can be followed for several kilometers (up to 7 km for some veins) and certain local enlargements have a thickness of 50 m. According to Rossovskij et al. ( 1974) it is possible to define several types of pegmatitic veins from their mineralogic composition:
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Oligoclase-microcline with black tourmaline and beryl.
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Albitized microcline with more frequent black tourmaline and beryl.
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Albitized microcline with black tourmaline, beryl and concentrations of lepidolite, multicolored tourmaline, spodumene, and pollucite.
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Albite with segregations of lepidolite and spodumene.
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Lepidolite, spodumene and albite.
Three types of veins (2, 3 and 5) are found in the Nilaw field. The central part of the third type of vein shows lepidolite, blue cleavelandite, multicolored tourmaline, kunzite (lilac-colored spodumene), white-pink spodumene, beryl and pollucite. Microlite, manganotantalite, columbite-tantalite and cassiterite are present there and also in type 5. Fuchs et al. (1974) advance the figure of 1,000 tons of reserve of beryl in the veins where it is exploitable in segregations. The average contents of Li, Cs, Rb and Sn are also appreciable (Rossovskij et al., 1974; Chmyriov et al.. 1975). The workings that we visited cut the pegmatites only in a place where the thickness of the vein is about 15 m. The zonation of this body is asymmetrical; fine grained in the lower levels, and in higher levels an assemblage of large size crystals, where quartz, microcline and spodumene dominate. The crystals of spodumene embedded in the rock are rosy and opaque, in immense sheafs with rather diffuse outlines. Crystal-lined cavities are mostly localized toward the top of the vein; those that we could examine are about 50 cm across and contain essentially large crystals of quartz and microcline. It is certain that they also contained crystals of kunzite as we saw elsewhere. Muscovite, black tourmaline and beryl are found in the matrix, as are also some phosphates of iron, manganese and lithium. At the top, limited to a layer 20 cm in thickness, the pegmatite is full of blades of columbite-tantalite. We have also noticed that the pegmatites at Nilaw, as at Mawi and Korgal, are invariably associated with amphibolites. |
