Kezra Venn pulled off her right mitten, tucked it into her belt. Then she pressed her bare fingertips directly against the upright joint inside the fissure.
In natural geology, when liquid fiery dark rock erupts through an older bed of sedimentary limestone, the heat of the molten rock bakes the surrounding stone for yards in every direction. The limestone recrystallizes into brittle, sugary marble, fractured by boiling steam and stained with dark ribbons of melted rock waste, iron crust, and sulfur ash. Geologists called it contact metamorphism—the violent, messy scar left whenever underground fire met water-laid stone.
Here, inside the heart of the Black Stone Tooth, there was no metamorphic zone at all.
Zero contact heat. Zero baking. Zero recrystallization.
The pale, fossil-flecked grey limestone met the glassy black dark rock along a seam so sharp and clean that it looked as though both rocks had been cut with a giant lapidary saw and pressed together like two planed boards of seasoned ash. Kezra ran her thumbnail down the line. Then, her nail crossed from the cool, chalky texture of the seabed settled mud to the slick, glassy hardness of the fiery pillar without catching on a single burr of fused melted rock waste.
