Fig. 3. Plagioclase crystals in this cathodoluminescent image are still closer to the myrmekite-bearing granite in strongly altered diorite that lacks hornblende (replaced by quartz). Abundant K-feldspar has not yet been introduced. Here, many plagioclase crystals have reversed zoning with sodic cores (pink) and relatively-calcic rims (beige grading to dark blue in center of crystals). Under cross-polarized light, the crystals are speckled but clear and lack any albite twinning. One crystal has a tiny island of K-feldspar (light blue, center of photo). Electron microprobe studies show that pink grains have rims An_17-20 and cores An1-5 while beige-grading-to-purple grains have cores and rims of An_17-20. In cores of some pink grains with sodic cores, silica is in excess of what would fit into a plagioclase feldspar structure, but no quartz is visible under cross polarized light. Also in some cores, probe analyses show that K₂O locally ranges from 1 to 50%, but no microcline is visible in cross-polarized light but may be seen in cathodoluminescence (not shown).