Eglestonite, [Hg 2 ] 3 Cl 3 O 2 H; confirmation of the chemical formula by neutron powder diffraction

To settle the discussion on the chemical formula of eglestonite, synthetic material was investigated by X-ray single crystal, neutron powder diffraction, and IR spectroscopic methods. The results show unequivocally that the chemical formula is [Hg2J3Cl302H, although no peaks attributable to the OH stretching vibration were observed in the powder IR absorption spectrum. From the good agreement between the structures of natural and synthetic eglestonite, as determined by X-ray single crystal methods, it is suggested that they have the same chemical formula. The formula of the Br-dominant isotypic mineral kadyrelite, for which Hg,(Br,Cl)20 was recently proposed, should also probably be modified to [Hg2J3(Br,Cl),o2H.