Symplectic texture occurs when two minerals grow simultaneously and interpenetrate each other, often resembling microscopic worms or fingerprints under a petrographic microscope. This texture usually forms during the cooling of igneous rocks or during high-grade metamorphism when an unstable mineral breaks down into two new phases. Geologists use these textures to determine the pressure and temperature history of the rock.
Heard on the job
The thin section reveals a symplectic intergrowth of quartz and feldspar along the grain boundaries.