Acta Musei Moraviae

Beryl-columbite pegmatite Věžná I

The beryl-columbite subtype Věžná I pegmatite has been subject of numerous scientific studies particularly from Petr Černý. It penetrates serpentinite and has a very complicated mineralogical evolution including several stages of crystallization. The primary magmatic crystallization includes formation of granitic zone, graphic zone, blocky zone with quartz core, as well as albite unit, which was previously considered metasomatic, and newly-defined albite-pollucite unit. The pegmatite body was subjected to several significant alteration processes such as kerolitization of quartz, alteration of primary minerals – phlogopite, cordierite, beryl, tourmaline and pollucite with rich assemblages of secondary minerals – e.g., vermiculite, muscovite, paragonite, phlogopite, beryl, smectite, aegirine, arfvedsonite, milarite, epidydimite, bertrandite and zeolites. External Mg-contamination proceded in several stages including pre- and post-emplacement contamination of pegmatite melt and Mg(Ca)-contamination related to most alteration processes. Věžná I pegmatite is commonly referred to as beryl-columbite subtype, but abundance of graphic textures, and composition of tourmaline (Mn-rich elbaite) and Li-mica (polylithionite) indicate relation to the elbaite subtype. A total of 59 minerals are currently known from the Věžná I pegmatite.