Gems and gem-bearing pegmatites of the Shigar valley, Skardu, Northern Pakistan
Abstract
Shigar valley, due to various semi- precious gemstones, is one of the most important valleys of the Baltistan in the northern areas of Pakistan. The gemstones mostly concentrate into the pockets or cavities of the zoned pegmatitic dikes or veins. The pegmatite bodies are intruded into the metasediments and meta. igneous rocks of the Karakorum Metamorphic Complex (KMC) and are considered as part of the Karakorum Axial Batholith.
The gemstones occurring in the pegmatitic bodies of the Shigar valley include: aquamarine, colorless to yellow topaz, green fluorite, tourmaline (schorl), garnet, fluoroapatite, morganite, goshenite, epidore, quartz etc. These gemstones are present into the cavities or pockets in the coarse- grained zones of the pegmatitic bodies. Internal structure, texture and mineralogy of these bodies are variable at different localities of the valley. Tourmaline (schorl) is ubiquitous in the entire gem- producing localities, while other gemstones are specific to certain localities. This suggests the role of variable geochemical conditions/parameters during the formation of gemstones within these pegmatites.
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