This is a type of spring with a bitter taste caused by bitter sulphate minerals. Shen Kuo, a scholar in Song Dynasty, in his book ‘A Note of Dream Brook’, stated ‘There is a bitter spring in Qianshan County in Xinzhou, where the spring flow forms a stream. Upon boiling, the water turns into danfan (chalcanthite), and upon further stewing, the danfan turns into copper, and the iron kettle also turns into copper upon prolonged stewing. It is amazing that water can turn into copper; the change of material is unpredictable’. In fact, the bitter spring described by Shen Kuo contained copper sulphate, and after evaporation, the copper precipitated into copper metal, which attached to the surface of the iron kettle.