Two different types of solid samples of bytownite (Ca0.7Na0.3Al2Si2O8 to Ca0.9Na0.1Al2Si2O8) composition were fabricated from synthetic crystal and glass powders. The crystal and the glass powders were produced by crystallisation or melting of a gel of bytownite composition. Cold pressing under vacuum followed by hot isostatic pressing (hip) of the powders produced fully dense samples composed either of 100% bytownite crystals or of 90% bytownite crystals and 10% bytownite glass. The cold-pressed samples were composed of a matrix of nanometer sized bytownite needles and larger crystals of up to 3 mu m in size. During hot pressing the grain sizes in the matrix increased slightly while larger crystals increased to close to 4 mu m. The rheological behaviour of the hot isostaticly pressed samples for cases of tri axial compression and torsion was tested in a gas confining deformation apparatus at high temperature and confining pressure. Grain growth was observed during the deformation experiments. The maximum flow stress was typically less than 200 MPa and was attained by sample strain of 10% during axial compression and a shear strain of 1.0 during torsion. The resulting microstructures were dominated by fibrous grains for the compressive deformation and by more round-shaped grain boundaries during torsion. Both type of experiments induced a preferred shape and crystallographic orientation.