Beryl (/ ˈ b ɛr əl / BERR-əl) is a mineral composed of beryllium aluminium silicate with the chemical formula Be 3 Al 2 Si 6 O 18. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is …