Soda ash was precipitated from T-brine solution (obtained from Botswana ash storage ponds) in the presence of four different habit modifiers namely, aluminum, silicate and Triton X-100 and calcium so as to investigate their effects on soda ash morphology and purity. Aluminum and calcium were found to be the best modifiers. Crystals were identified and characterised using X-ray diffraction, environmental scanning electron microscopy and energy dispersive spectroscopy. A control sample of T-brine with no modifier, produced fine needles. Different morphologies, ranging from cylindrical through twinned cylinders to inter-grown aggregates, were observed in the presence of the different additives. The rod shaped crystals containing Triton X-100 occluded about 0.86% Cl while aluminum and calcium occluded the least, each 0.22% Cl. (C) 2003 Elsevier B.V. All rights reserved.