Despite their high boron contents, some boron deposits in Turkiye contain considerable amountS of arsenic. Arsenic in boron minerals receives penalty in marketing and thus its removal is necessary. Since colemanite undergoes decrepitation at temperatures near its decomposition, the objective of this study was to determine the extent of arsenic removal through the decrepitation of colemanite ores with high As content. The effect of temperature, retention time, and particle size range was investigated and the degree of arsenic removal and the quality of colemanite concentrate were quantified. The results reveal that arsenic removals of 95-98% with As levels as low as 0.02% in the colemanite concentrate are achieved. (C) 1999 Elsevier Science S.A. All rights reserved.