Shen Xitang’s fingertips brushed across the fractured core of the Chiyan Sand, where magnetite powder had gathered along the crystalline facets in radial patterns.
Xiao Jingming aligned the improved armillary sphere with a crevice in the roof of the mine cave. The bronze gnomon cast a slender shadow through the sulfur vapor, pointing directly to the "Xu-3" ore vein marked in the *Secret Record of River Defense*.
"This Chiyan Sand has been stored for at least five years," Shen Xitang said, scraping saltpeter crystals from the cave wall and placing them into a glass distiller.
Chapter 49