<b>Self-healing</b><b> mineral film</b><b>on</b><b> sandstone</b><b>: implication for conservation and environmental monitoring</b>

Despite experiencing thousands of years of wind and rain, some stone carvings have remained remarkably well-preserved. Understanding the reasons behind this, particularly in the context of climate change and escalating air pollution, holds significant importance for understanding the evolution of geological materials. Here we discovered a black to reddish-brown, relatively dense mineral film with a thickness of approximately 150 μm on the surface of sandstone.