The Canadian Mineralogist Vol. 54, pp. 1033-1041 (2016) DOI: 10.3749/canmin.1500112 ON THE CRYSTAL-CHEMISTRY OF BJAREBYITE, BaMn 2 þ 2 Al 2 (PO 4 ) 3 (OH) 3 , FROM THE PALERMO #1 PEGMATITE, GRAFTON COUNTY, NEW HAMPSHIRE, USA NICOLA ROTIROTI Universit` a degli Studi di Milano, Dipartimento di Scienze della Terra ‘‘A. Desio’’, via Botticelli 23, 20133, Milano, Italy PIETRO VIGNOLA § Consiglio Nazionale delle Ricerche, Istituto per la Dinamica dei Processi Ambientali, via Botticelli 23, 20133, Milano, Italy DANILO BERSANI Dipartimento di Fisica e Scienze della Terra, Universit` a di Parma, Viale G.P. Usberti 7/a, 43124 Parma, Italy WILLIAM B. SIMMONS, ALEXANDER U. FALSTER, AND ROBERT W. WHITMORE Maine Gem and Mineral Museum, PO Box 500, 99 Main St, Bethel, Maine 04217, U.S.A. JAMES W. NIZAMOFF Omya, Inc 39 Main Street, Proctor, Vermont 05765, U.S.A. PAOLO LOTTI, ANDREA RISPLENDENTE, AND ALESSANDRO PAVESE Universit` a degli Studi di Milano, Dipartimento di Scienze della Terra ‘‘A. Desio’’, via Botticelli 23, 20133, Milano, Italy ABSTRACT Bjarebyite, BaMn 2þ 2 Al 2 (PO 4 ) 3 (OH) 3 , is a rare secondary phosphate mineral in granitic pegmatites. From the crystallographic point of view it is exhaustively described in the monoclinic unit cell with a 9.0671(2) ˚ A, b 12.1500(4) ˚ A, c 4.9403(1) ˚ A, b 100.399(2)8, V 535.31(2) ˚ A 3 , and space group P2 1 /m. Single crystal X-ray diffraction data were collected with MoKa radiation. The hydrogen positions were located by difference Fourier map and refined in the final steps of the crystal structure anisotropic refinement, leading to an R index of 1.99%. A very good agreement was found with microprobe chemical analyses and bond valence calculations which show expected values for all the atomic sites. These features were confirmed by comparing the Raman spectra of bjarebyite and kulanite. Keywords: bjarebyite, pegmatite phosphate, single-crystal X-ray diffraction, hydrogen bonding. INTRODUCTION Bjarebyite, BaMn 2 þ 2 Al 2 (PO 4 ) 3 (OH) 3 , is an ex- tremely rare secondary phosphate mineral discovered and described for the first time at the Palermo #1 pegmatite, North Groton, Grafton County, New Hampshire, U.S.A. (Moore et al. 1973). As pointed out by Paul Brian Moore, the ‘‘exchange reactions between triphylite and adjacent amblygonite produced compounds such as scorzalite and childrenite. Intro- duction of Ba 2 þ and Sr 2 þ at this stage resulted in such exotica as palermoite and bjarebyite’’. The mineral was found in a complex association within a metasomatized amblygonite-scorzalite mass as crys- tals in open cavities. § Corresponding author e-mail address: pietro.vignola@idpa.cnr.it, pietroevignola@gmail.com 1033