Lepidocrocite electron micrograph

As lepidocrocite is metastable relative to goethite, it can be expected that lepidocrocite may transform into goethite. As demonstrated in the laboratory, this transformation proceeds via solution (see Chap. 14). Electron micrographs from a redoxi-morphic soil in Australia indicate that the same process seems to occur in soils (Fig. 16.5). The lepidocrocite crystals show dissolution features and there are small, acicu-lar, goethite crystals in their neighbourhood. Feroxyhyte was reported in two allopha-... 

Fig. 16.5 Electron micrographs of an association of lepidocrocite (Lp) with goethite (Gt) from a redoximorphic soil, Natal, South Africa (courtesy P. Self).

Fig. 16.9 Electron micrographs of soil lepidocro-cite. a) Large multidomainic lath-like crystal viewed perpendicularto [001] with laminar pores from a re-doximorphic soil, Natal, South Africa, b) Poorly crystalline grassy lepidocrocite crystals mixed with tiny ferrihydrite particles and pseudo-hexagonal kaolinite platelets. Origin as before (a. b courtesy P. Self), c) Small lepidocrocite crystal from a hydromorphic soil (with ferrihydrite) viewed perpendicularto [001] and showing (020) lattice fringes (see also Schwert-mann. Taylor, 1989,with permission).

Fig. 18.5 Scanning electron micrograph of a tubercle from a corroded water pipe showing large hexagonal plates or prisms of green rust and small Fe " oxide crystals, probably lepidocrocite and goethite formed from oxidation of green rust (Bigham and Tuovinen, 1985, with permission, courtesy J. M. Bigham).

Figure 1.4. (a) Scanning electron micrograph of a fractured cross section of a mineralized tooth from the radula in Fig. 1.1. (b) Enlargement of the upper part of the same fractured cross section. The magnetite layer (M) lines the interior surface. The thick dahllite layer (D) is on the exterior. The thin lepidocrocite layer (L) is sandwiched between the two. C, organic sheath and cell remnants. 

Fig. 6-2. X-ray diffractogram (upper), infra red spectrum (middle) and electron micrograph (lower) of lepidocrocite.

Figure 5. Electron micrograph taken after 298 days aging of Run 5, showing lath-like lepidocrocite crystals and smaller needle-like goethite crystals...

Figure 7. Electron micrograph taken after 302 days9 aging at Run 4, showing compact crystalline intergrowth of goethite and lepidocrocite...

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