Introduction

Raman and structural comparison between the new gemstone pezzottaite Cs(Be2Li)Al2Si6O18 and Cs‐beryl

“…[1][2][3] It is considered a member of the 'beryl group', along with beryl sensu stricto (Be 3 Al 2 Si 6 O 18 ), [4,5] bazzite (Be 3 Sc 2 Si 6 O 18 ), [6] stoppaniite (Be 3 Fe 2 Si 6 O 18 ), [7,8] and indialite (Mg 2 Al 3 AlSi 5 O 18 ). [3] Chemical and gemological features of pezzottaite from the Sakavalana granitic pegmatite located near Ambatovita (Madagascar), along with a geological description of the deposit, were described by Laurs et al [1] and Hawthorne et al [2] Pezzottaite and beryl are not isostructural: Pezzottaite is trigonal (space group R3c), and beryl is hexagonal (space group P6/mcc). [9,10] However, their structures show several similarities, both consisting of six-membered rings of SiO 4 tetrahedra, perpendicular to the [0001] axis, linked by AlO 6 octahedra and (Li,Be)O 4 tetrahedra to form a three-dimensional framework.…”

“…Pezzottaite is a rare Cs‐bearing mineral with ideal composition Cs(Be 2 Li)Al 2 Si 6 O 18 , discovered on November 2002 . It is considered a member of the ‘beryl group’, along with beryl sensu stricto (Be 3 Al 2 Si 6 O 18 ), bazzite (Be 3 Sc 2 Si 6 O 18 ), stoppaniite (Be 3 Fe 2 Si 6 O 18 ), and indialite (Mg 2 Al 3 AlSi 5 O 18 ) . Chemical and gemological features of pezzottaite from the Sakavalana granitic pegmatite located near Ambatovita (Madagascar), along with a geological description of the deposit, were described by Laurs et al .…”

“…The amount of alkali governing the change of symmetry (i.e. from trigonal to hexagonal) is still dubious, and Pezzotta suggested that pezzottaite contains Cs 2 O > 9 wt%.…”