Ji Xiaoying got up from the ground, holding a black stone in her hand. This stone was even blacker than the one she picked up last time, so black that it shone under the sun. She rubbed her aching butt as she faced the black stone.
Su Qing was pleasantly surprised when she saw the stone in Ji Xiaoying's hand. Was it coal?
Since they could pick up coal, this mountain must have a coal mine. They would not suffer from the cold with coal when they went to Jingshi Dao. They could even sell it for money. This was an inexhaustible treasure.
Su Qing searched her memory. The Great Xia Kingdom did not know about coal. In modern times, private coal mines were already rich enough to rival a country! The ordinary people used wood for heating, and the palace used charcoal for heating.