Mineralization epitaxy

The physical stmcture of mixed-layer minerals is open to question. In the traditional view, the MacEwan crystallite is a combination of 1.0 nm (10 E) non-expandable units (iUite) that forms as an epitaxial growth on 1.7 nm expandable units (smectite) that yield a coherent diffraction pattern (37). This view is challenged by the fundamental particle hypothesis which is based on the existence of fundamental particles of different thickness (160—162). 

Figure 5b. Mineral aurichalcite calcined at 350 C for 4 hours. Schematic diagram showing epitaxial registry and similarities of d-spacinqs for the most intense aurichalcite and ZnO diffraction spots, n = ZnO with [3031] zone axis, ZnO with [1010] zone axis, and Q " aurichalcite near [101] zone axis. A = aurichalcite.

McPherson, A. and Shlichta, P. (1988). Heterogeneous and epitaxial nucleation of protein crystals on mineral surfaces. Science 239, 385-387. 

Fig. 16.19 Electron micrographs of natural associations between iron oxides and other soil minerals, a) Goethite (Co) crystals epitaxially grown on kaolinite (K) flakes (TEM) from a late-rite in Cameroon (courtesy J.P. Muller see also Boudeulle, Muller, 1988). b) Association of kaolinite (k), goethite (go) and hematite (he) in an Oxisol, Cameroon (SEM) (1987 courtesy J.P. Muller see Muller, Bocquier, 1986). c) Goethite accumulation between kaolinite...

I. Sunagawa, Vapor growth and epitaxy of minerals and synthetic crystals,/. Crystal Growth,45,1978,3-12... 

Figure 7.12. Examples of epitaxy observed in minerals, (a) lyrite on marcasite (b) quartz on calcite (c) albite on orthoclase.

Organic matrices with a capactiy to act as morphological catalyst in the deposition of minerals must consequently be crystalline in nature. In the literature, colloidal or amorphous phases are frequently postulated as organic starting materials in biomineralization. Such a viewpoint, however, is not consistent with oriented epitaxial growth. 

The attachment of the MM to the CP will activate the mineralizing substrate and calcium carbonate crystals are laid down in epitaxial order. Crystal growth terminates upon secretion of a newly formed MM on the growing crystal surface whereby a kind of organic blanket is formed. Subsequently, CP becomes attached to MM. A sand-... 

Epitaxial crystallization of polymers has been investigated for a wide variety of substrates minerals (alkali halides, talc, mica, and so on), low molecular weight organic materials (condensed and linear aromatics, benzoic acid and many of its substituted variants and their salts or hemiacids, other organic molecules of different types), and other crystalline polymers. 

The mineral spinel, MgA Of, was one of the first substrates tried for GaN epitaxy [8,25,35], and has been the most successful of all alternative substrates for GaN heteroepitaxy. Spinel single crystals can be grown by the Czochralski technique and substrates of modest size can be obtained commercially. The chief advantage of spinel over sapphire is that it cleaves more easily than sapphire. 

Rancourt and Scorzelli suggested the mineral name antitaenite for the LM phase and proposed that it may be stabilized by an epitaxial interaction with tetrataenite, since it is always found in microstructural association with the latter phase and with an indistinguishable lattice parameter. 

Rancourt DG, Ping JY, Berman RG (1994) Mossbauer spectroscopy of minerals. III. Octahedral-site Fe quadrapole splitting distributions in the phlogopite-annite series. Phys Chem Minerals 21 258-267 Rancourt DG, Scorzelli RB (1995) Low-spin Y-Fe-Ni(YLs) proposed as a new mineral in Fe-Ni-bearing meteorites Epitaxial intergrowth of yls and tetrataenite as a possible equilibrium state at 20-40 at % Ni. J Magnet Magnetic Mater 150 30-36... 

Rieder M, Cavazzini G, D yakonov YuS, Frank-Kamenetskii VA, Gottardi G, Guggenheim S, Koval PV, Muller G, Neiva AMR, Radoslowich EW, Robert JL, Sassi FP, Takeda H, Weiss Z, Wones DR (1998) Nomenclature of the micas. Clays and Clay Miner 46 586-595 Royer L (1928) Recherches experimentales sia I epitaxie ou orientation mutuelle de cristaux d especes differentes. Bitll Soc frang Miner Crist 51 7-l 59... 

Hazemann J-L, Manceau A, Sainctavit P, Malgrange C (1992) Structure of the a-FexAlixOOH solid solution. I. Evidence by polarized EXAFS for an epitaxial growth of hematite-like clusters in Fe-diaspore. Phys Chem Minerals 19 25-38... 

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