Figure F36. Photomicrographs of Thin Section 257 (Sample 324-U1349A-15R-6, 42–44 cm) in Unit V, Hole U1349A. A. Unusually large Cr spinel crystal aggregate set in a sheaf-spherulitic matrix. The aggregate has a skeletal appearance, but this morphology is not borne out by closer inspection. B. Grain consisting of differently oriented crystals with miscellaneous shapes in cross section. Note the high percentage of reflective plagioclase (gray) and clinopyroxene (lighter gray) within the interior of the aggregate. The silicates are coarser grained than they are in the spherulitic matrix outside the aggregate (upper right). C. Enlarged view of a portion of the interior of the aggregate. The brown spinel is arranged in clusters that are not part of a larger skeletal structure. Many tiny crystals of unaltered Cr spinel with cubic or diamond-shaped morphologies make up each cluster, and these have diverse shapes. A and C are under transmitted light; B is under reflected light.
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