May I congratulate Messrs. Edmunds and Morgan-Jones on their paper on the Geochemistry of Groundwaters in British Triassic Sandstones. They have amassed a useful mine of data in an area where it is urgently needed, and gone a long way in interpreting the results.
May I comment in just one area, namely that concerned with the mineralogy of the sandstones, and, specifically, the first paragraph of that section (page 78) in the paper. The material on iron oxides there given seems unclear in that it is not made clear what is conjecture and what is experimentally established fact.
In particular, the redness of the sandstone is attributed to “haematite, goethite and a variety of amorphous hydrated ferric oxides”. Later, we are informed that “the iron present in the sandstone is in a hydrous, amorphous form, approximately FeO(OH)”. What, please, is the experimental evidence for these statements, when the X-ray analysis consistently shows only haematite?
If the authors suspect other oxides from microscope studies, unsupported by X-ray evidence, then I suggest that “haematite was confirmed and limonite was suspected” would cover the situation, where limonite has the meaning defined by Deer, Howie and Zussman i.e. “hydrated oxides of iron with poorly crystalline characters whose real identity is not known”.
- © The Geological Society, London 1977