The first neutron powder refinement of the monoclinic Ca-analcime wair
akite, Ca(AlSi2O6 . H2O)(2) is presented. The refinement is sensitive
to water and cation occupancy but only slightly sensitive to water rot
ation. Within the limits of the refinement the data support a model in
which the water dipole points away from the cation as is physically r
easonable, but in which the water shows orientational isotropy about t
he water-cation axis.