Mine fungus

A species of Fibroporia.

This fungus thrives on the timber of coniferous trees, like pine, when conditions are moist, specifically with a wood moisture content ranging from 40% to 50%. In environments with high humidity, its white, cotton-like mycelial growth can extend across wood surfaces and even bridge non-nutritive substrates. Freshly developed mycelium may exhibit small droplets of transparent liquid. Its ideal growth temperature is 28 °C (82 °F), though it can proliferate in temperatures spanning from 3 to 36 °C (37 to 97 °F). The fungal fruiting structure manifests as an uneven white plate, measuring between 2 and 12 mm in thickness.