Ferrihydrite colour

Fig. 6.10 Left Placement of various synthetic goethites (G), lepidocrocites (L) and hematites (H) in CIE L a b colour space. Right Development of a and b in the CIE L a b colour space during the transformation of ferrihydrite (common starting point) to goethite or hematite, respectively (Nagano et al., 1994, with permission).

Fig. 6.11 Munsell colours of synthetic hematite, ferrihydrite, lepidocrocite, and goethite samples (Courtesy A.C.Scheinost Scheffer Schachtschabel,...

YR with values >6 for lepidocrocite and <6 for ferrihydrite. These ranges are caused mainly by a variation in crystal size. Upon cementation into dense, hard masses all these colours darken (lower value) and reliable identification requires grinding. 

Plate 13.1 The colour changes of the ochreous precipitates formed from ferrifer- water-pH of 3.7 on the right to 2-line ferrihydrite after neutralization by a ous acid mine water from a lignite mine near Sokolov, Czech Republic, and their pH 8.2-water on the left side (arrows) (Courtesy E. Murad Murad Rojik, X-ray patterns clearly indicate the abrupt transition from schwertmannite at a 2003, with permission). 

Plate 16.1 a) Soil profile coloured by goethite (Ochrept, France), b) Soil profile coloured by hematite (Ultisol, Brazil), c) Soil profile coloured by lepidocrocite (Aquept, South Africa), d) Ferrihydrite formation by oxidation of Fe " in water seeping out of a Cley. 

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