|Figure 9-2. Zone of microcrystalline CaCO3 (M) into which and through which crystals of columnar calcite (C) pass . This image was generated with cross-polarized light with a gypsum plate in the light path to emphasize the continuity of crystals; any one crystal is one shade of purple. Thus the area labelled C1 extending from the top to the bottom of the image is one crystal. A
corresponding image in plane-polarized light shows the apparent original continuity of the microcrystalline zone. The passage of crystals like C2 and C1 into and through the microcrystalline zone suggests that the microcrystalline material has been recrystallized by aggradation of the columnar calcite.
Another pair of plane-light and cross-polarized light images illustrate another example of evidence for recrystallization of microcrystalline CaCO3 to columnar calcite in this speleothem.
Photomicrograph was taken in cross-polarized light with a gypsum plate; 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.
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