pegmatitischen

Pegmatitisch is an adjective used in geology to describe rocks, textures, and mineral assemblages characteristic of pegmatites. It refers to the highly coarse-grained nature and the unusual mineral content that distinguish pegmatites from ordinary granitic rocks. The term is applied to the rocks themselves as well as to late-stage processes and features associated with them.

Pegmatites form during the final stages of crystallization of granitic magmas. They crystallize from volatile-rich residual melts that become enriched in incompatible elements like lithium, beryllium, tantalum, niobium and rare earths. The high volatile content promotes the growth of exceptionally large crystals, yielding a texture in which individual crystals may range from centimeters to meters in size. Micas, quartz and potassium feldspar are commonly dominant, with accessory minerals such as tourmaline, beryl, spodumene, cassiterite and various Ta-Nb oxides.

Mineralogy and textures often include a clear separation between coarse-grained mineral assemblages and more orientated, vein-like zones. Pegmatites may host giant crystals and, in some deposits, gem-quality minerals. The rocks can form as intrusions that cut through surrounding rocks, or as dikes and pockets within granitic bodies. They are widely distributed globally and frequently occur in granitic batholiths or incompatible-element-enriched margins.

Economic and scientific relevance is high. Pegmatites are important sources of lithium, beryllium, tantalum, niobium and tin, and they yield prized gemstones and minerals for collecting. Their study provides insights into crustal differentiation, volatile-rich magmatic processes, and the concentration mechanisms that produce extreme grain sizes.