X-ray observations on wairakite and non-cubic analcime

Mr. A. Steiner has kindly invited the present writer to study by X-ray methods the new mineral wairakite described by him in the preceding pages. The material provided includes an incomplete octahedron 15 ram. across with small modifying ieositetrahedron-like faces, and some smaller partial icositetrahedra. Faces are dull and give diffuse reflections oil the optical goniometer, but, by attaching small pieces of glass cover-slip to improve the reflections, interfacial angles approximating to those of the cubic forms {111} and {211} were measured. As pointed out by Mr. Steiner, however, the mineral is birefring'ent, biaxial, and finely twinned. A preliminary small-diameter X-ray powder photograph taken by Mr. N. Wells of the Soil Bureau, Wellington, showed an apparently cubic, analeime-like pattern (personal communication).