It is with infinite sadness that I write these lines.

I first met Udo Schwertmann in the spring of 1975. His department was seeking a scientist with experience in X-ray methods (XRD and XRF) and I was looking for a job. To me, a young upstart with a PhD and experience in igneous petrology and geochemistry, soils were something like ‘yukk’. In the end, Schwertmann taught me to respect soils and practically all that I know about soils and clays.

First, the sheer size of this 2-metre tall, wiry man was impressive. Then there was the reserved dignity of the...

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