The rare metals beryllium, lithium, tantalum and niobium and alloys made from them have a wide variety of uses and have become increasingly important in today's technology driven society. For example all are used in the aircraft industry and lithium and niobium also have nuclear applications.
Rare metals in Afghanistan
There are currently a total of 49 recorded occurrences of these metals in the Afghan mineral occurrence database, all occurring in pegmatitic rocks. Initial prospecting was completed in the 1960s and 70s and identified the areas discussed below, but further exploration will be necessary to prove the existence of economically significant deposits.
Eight pegmatite fields with beryllium mineralisation have been identified to date in the Laghman and Nangarhar provinces. The mineralisation is typically related to either Oligocene or Early Cretaceous magmatism, being hosted in the surrounding metasediments. The most detailed work was conducted at the Darrahe-Pech deposit, where beryl crystals up to 40 cm across have been discovered and category C1+C2 resources of 12 000 t of beryl (containing 1 480 t of beryllium oxide) have been estimated. The beryllium (and lithium) mineralisation is associated with albitised-microcline and spodumene-albite pegmatites. Coarse beryl has also been produced at the Darrahe-Nur deposit.
Twelve pegmatite fields with lithium mineralisation have been identified to date in Laghman and Nangarhar provinces, but also in Badakhshan and Uruzgan provinces. Again the mineralisation occurs in pegmatites hosted in variably aged metasediments, typically intruded by Oligocene granitoids. The most thoroughly evaluated area is the Parun pegmatite field (Nangarhar province), where seven separate mineralised zones have been recognised. Four pegmatite types have been recognised in the area, with the spodumene-albite(- microcline) type being the most economically significant and typically grading around 1.5% lithium oxide. Only speculative resources were estimated and the area clearly deserves more detailed exploration. The same is true for the Taghawkor prospect in Uruzgan, where five pegmatite dykes assay between 1.7 and 2.8% lithium oxide.
Tantalum and Niobium
Fourteen pegmatite fields with tantalum and niobium mineralisation have been identified to date, with eleven of these also containing beryllium or lithium mineralisation. The remaining three are located in Parwan and Badakhshan provinces. The prospect with the greatest potential is Nilaw in Laghman province. Here three types of pegmatite cross-cut Early Cretaceous gabbros and diorites. Individual pegmatites up to 4 km long and 4 m wide have been discovered, containing beryllium, lithium, tantalum, niobium, cessium, rubidium and tin. Systematic exploration will be necessary to determine the economic viability of the prospect.