PegmatitLagerstätten

PegmatitLagerstätten, or pegmatite ore deposits, are extremely coarse-grained igneous rocks that crystallize late in granitic magmatism. They form dikes, pockets, or veins within granitic intrusions and host crystals that can reach decimeters in size. A defining feature is a high volatile content and enrichment in incompatible elements, producing rapid, layered crystallization and a diverse mineral assemblage. Pegmatites typically show strong zoning from core to rim.

Mineralogy and economic importance: The bulk consists of quartz and alkali feldspar, but accessory minerals are diverse. Lithium-bearing minerals (spodumene, petalite, lepidolite) are especially important, along with beryl, tourmaline, cassiterite, and columbite-tantalite. Pegmatites are major sources of lithium, tantalum, niobium, and beryllium, and yield gemstones such as tourmaline and aquamarine in favorable samples. Extraction is usually open-pit or underground, guided by zoning patterns and indicator minerals.

Formation and distribution: Pegmatites form during late-stage crystallization of granitic magmas when melts concentrate volatiles and incompatible elements. The resulting deposits are distributed worldwide, especially in continental crust that hosts granitic belts, with many occurrences in older shield areas. Their study informs models of ore formation and the behavior of volatiles in crustal magmas.