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E. Anhedral, partly resorbed, phenocryst in weakly-altered porphyry. This photomicrograph shows the maximum pleochroic color (dark brown) of magmatic biotites from the Ok Tedi Intrusive Complex. The green fibrous mineral at the center is chlorite which has replaced biotite. Two large phenocrysts of magnetite that were partly, or totally, enclosed by the biotite are visible in the center of the photo. Additional small granular crystals of magnetite form a fringe around parts of the perimeter of the biotite. The field of view is about 0.8 x 1.2 mm. Plane-polar light. JDD-94-10