Conversion of carbonate grains to fluorite gives a microporous pseudomorph in which the contained organic material may be dyed and observed. Photographs illustrate the application of this technique to in-situ observation of perforating algae and other organisms in modern Bahama ooids and skeletal grains. A similar group of organisms, that demonstrates the preservation of detailed cellular structure at least from Pleistocene time, has been found in Miami Oolite ooids. Other possible applications are to ancient carbonates and to carbonates trapped by blue-green algae.

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