|Figure 9-10. Layer of microcrystalline CaCO3 (M) between columnar calcite (C) above and below. Note the gradation from the completely microcrystalline zone (M) to continuous layers (arrow 1) to discontinous layers (arrow 2) to very subtle layering (arrow 3). A corresponding image in cross-polarized light shows that individual columnar calcite crystals extend from below the microcrystalline zone to above it. If such continuity is evidence of recrystallization of microcrystalline material to columnar calcite, recrystallization may also explain the discontinuous and/or subtle layering that is visible at the arrows.
Photomicrograph was taken in plane-polarized light; field of view is 2.3 mm wide. Cumberland Caverns, Tennessee, U.S.A., Mody Dick formation; thin section CuMa. Sample collected by Mr. Ethan A. Goddard.
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