- © The Mineralogical Society Of America
A major interest in beryllium minerals, which are rock-forming constituents in certain metamorphic, hydrothermal and igneous environments, comes from their use as ore materials for Be, as single-crystal material for special optical purposes, and as gemstones. Beryl, ideally Al2Be3Si6O18, bertrandite, Be4Si2O7(OH)2, and phenakite, Be2SiO4 are mined and processed as ores of Be. Beryl and chrysoberyl are used as maser and laser crystals, and bromellite BeO has outstanding properties such as exceptionally high electrical conductivity and speed-of-sound propagation in combination with great strength and chemical resistance. Be-minerals find wide use as gemstones; emerald and alexandrite are among the most highly prized. For all these reasons, a large amount of experimental work has been reported on the synthesis of these minerals.
The interest in Be-minerals for petrology comes from the fact that Be can be a minor component in several rock-forming silicates such as sapphirine, margarite, and cordierite, and can have an important influence on the phase relations of these minerals. The study of the behavior of Be and Be-minerals may give an important insight in the history of magmatic and metamorphic rocks. One of the key questions for the natural occurrences is the problem of enrichment of Be, so that either Be-minerals can be formed or that common rock-forming minerals such as cordierite contain an appreciable amount of Be.
We start with a review of experimental work about synthesis of Be-minerals in various simplified systems, their phase equilibria, and their compositional variation. Thermodynamic data and calorimetric work are reviewed by Barton and Young (this volume). In the second part we review the geological setting and mineralogical characteristics of Be-mineralizations in regional metamorphic terrains and on hydrothermal Be-occurrences. Metamorphosed Be-rich pegmatites, leucogranites and …