Cymrite, a new barium mineral from the Benallt manganese mine, Rhiw, Carnarvonshire

Abstract

Among the specimens collected at the Benallt manganese mine in 1944 by Dr. A. W. Groves and myself was one (B.M. 1944,48) from the 60-foot level in no. 1 ore-body which showed on a face of dark, compact manganese ore colourless plates up to 7 mm. across and about ½ mm. thick. These plates proved to be uniaxial and negative with perfect basal cleavage. Heated in an ignition tube the fragments decrepirated, gave off water, and became pearly, white, and opaque. Qualitative tests showed Ba, Al, and SiO2 to be present. Preliminary X-ray photographs revealed hexagonal symmetry, but could not be matched with those of any known mineral.