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In Quaternary aeolian sediments, the relationship between sediment age, environment and degree of ’redness’ has generated considerable debate. One major difficulty that can hamper such studies is the ability to quantify the various iron oxide components within such sediments. Results of high field (9 T) rock magnetic measurements and Mossbauer spectroscopic analyses of samples from the Namib Sand Sea are presented in this paper. The results suggest that environmental magnetic measurements provide a sensitive means of quantifying the primary, source-rock-derived, iron mineral assemblage within such sediments. Isolation of the magnetic signal from the ’secondary’, fine-grained iron mineral assemblage that is present as part of the grain coatings, and which exerts a strong control upon sediment colour, is more problematic. The current data suggest that both haematite and goethite are present within the grain coatings. Copyright (C) 2000 John Wiley & Sons, Ltd.