052 Migmatite / Gneiss

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This rock is a migmatite, which is a fusion of metamorphic and igneous rocks. It forms when a partially melted metamorphic rock crystallizes into an igneous rock, combining the unmelted metamorphic part with the recrystallized igneous part. The lightest-colored portion of migmatite, comprising quartz and feldspars, was partially melted, while the darker section consists of biotites that remained largely unchanged from the parent rock. Quartz and feldspars display fine to medium-sized crystals (0.5-1mm), whereas biotites are characterized by a fine texture. Gneiss is a banded rock that features light-colored quartz and feldspars with fine to medium crystal sizes (0.5-1mm). In contrast, the darker sections contain fine-sized biotite minerals.