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Figure 3-3. Chalcedony in a layer outlined by dashed red lines. The black-and-white (to slightly yellow) birefringence is typical of silica minerals; the fibrous crystals visible here (e.g., at arrows) are a defining feature of chalcedony. This photomicrograph is a high-magnification view of a layer shown in a lower-magnification view in plane-polarized light and in a lower-magnification view in cross-polarized light. Photomicrograph was taken in cross-polarized light; field of view is 0.25 mm wide. Carlsbad Caverns, New Mexico, U.S.A; Georgia Giant stalagmite; thin section CB64. |
