Authigenic dolomite on marble surface

Abstract

The formation of dolomite remains controversial. Various hypotheses have been proposed, including primary precipitation from seawater, authigenesis or penecontemporaneous alteration of CaCO₃ by seawater, and postdiagenetic secondary replacement of CaCO₃ by groundwater, connate water, or other solutions. Although the existence of authigenic dolomite in recent sediments has been confirmed^1–3, all attempts to synthesize ordered dolomite at temperatures of sedimentary environments have failed⁴. It has been suggested that organic material^5,6 and clay minerals^7,8 may be important in the formation mechanism of dolomite. Here we present evidence that authigenic dolomite is formed on marble surfaces exposed to urban atmospheres. This discovery suggests that a relatively short period of time (of the order of a century) is actually required for dolomite formation in the natural system described here.