Figure 4-7. Microcrystalline CaCO3 in a stalactite from Namibia. This microcrystalline CaCO3 varies from dense (large M near top) to light and diffuse (small Ms near bottom) to peloidal (arrow), and the less dense material is interspersed with clear calcite (C). One area of the denser calcite may have been bored (B). The enclosure of clear calcite within microcrystalline crusts (as at the small Ms) suggests biological mediation of the formation of the microcrystalline CaCO3. A similarly highly differentiated microcrystalline fabric can be seen in an image of another stalactite.    Photomicrograph was taken in plane-polarized light; field of view is 2.3 mm wide. Guinas Cave, Namibia; Sample G95-2; thin section G95-2A. Sample collected by Dr. George A. Brook.
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