Figure 9-1. Zone of microcrystalline CaCO3 (M) with large detrital grains (arrows), over a zone of columnar calcite (C). Note the apparent continuity of this microcrystalline zone from the arrowed area into the area enclosed by the red loop. A corresponding image in cross-polarized light shows that some crystals of the underlying columnar calcite extend into and even through the microcrystalline zone, including the area in the red loop.
     Photomicrograph was taken in plane-polarized light; field of view is 2.3 mm wide. Carthage, Tennessee, U.S.A.; Flowstone MR68; thin section MR68. Sample collected from highway construction debris by L. Bruce Railsback.
  Speleothem Image
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