Electron microscopy genesis

Daulton T. L., Eisenhour D. D., Bernatowicz T. J., Lewis R. S., and Buseck P. (1996) Genesis of presolar diamonds comparative high-resolution transmission electron microscopy study of meteoritic and terrestrial nano-dia-monds. Geochim. Cosmochim. Acta 60, 4853—4872. 

Rock varnish (often called desert varnish when seen in drylands) is a paper-thin mixture of about two-thirds clay minerals cemented to the host rock by typically one-fifth manganese and iron oxyhydroxides. Upon examination with secondary and backscattered electron microscopy, the accretionary nature of rock varnish becomes obvious, as does its basic layered texture imposed by clay minerals (Dorn and Oberlander, 1982). Manganese enhancement, two orders of magnitude above crustal values, remains the geochemical anomaly of rock varnish and a key to understanding its genesis. 

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