The name chrysoberyl is derived from the Greek words chrysos and berullos, meaning "golden" and "gem crystal". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones. Members of the beryl group include emerald, aquamarine, and morganite while members of the chrysoberyl group include chrysoberyl, cymaphane (cat´s eye) and alexandrite. Beryl is a silicate with chemical composition Be3Al2(SiO3)6 and chrysoberyl is an oxide with composition BeAl2O4. Although both beryl and chrysoberyl contain beryllium, they are separate gemstone species unrelated in any other way. Beryl crystallizes hexagonally while chrysoberyl crystallizes in orthorhombic arrangements. Chrysoberyl will crystallize at higher temperatures than beryl. With cooling temperatures and increasing water activity, it will react with K-spar to form beryl + muscovite. Thus after chrysoberyl crystallizes in Be-rich pegmatites that intrude ultramafic hosts, tectonometamorphic events often result in metamorphic overprint. During crystallization of the pegmatite, much beryllium can be accommodated into the common rock-forming minerals of the pegmatite leaving little of the metal to form minor amounts of either beryl or chrysoberyl.