Each ring records a shift in mineral saturation, traceable to the exact season of deposition across millennia of hydrothermal cycling.
Pressure as author
Compression at 2.4 kilobars reshapes the crystal lattice, leaving signature stress-fracture patterns readable under cross-polarized light.
Light through layers
Thin-section polarized microscopy exposes band chemistry invisible to the unaided eye — iron gradients, silica phase transitions, trace-element ghosts.
Time, not age
Growth rate varies with hydrothermal input — a single centimeter of banding may span ten thousand years of quiet crystallization.