In 1983 found a mixture of ultramicro native lead and native tin in volcanic tuff in the west of Liaoning province.The mineral looks black-grey with many blue and purple points on it. In general, the mixture minerals pre- sent tabula and strip mode. It shows metallic luster. Moss scale of hardness is 1.5. Under the microscope, it appears weak heteropic. The reflective power is about 65%. Under a double-axle Camera, the single-grain minerals; are considered mic- rolitic aggregate by analyzing with X-ray diffraction. The obtainted debye patterns are the fold of native lead and native tin. Studing the minerals with energy spectrum and rapid electron probe scan proves that: the minerals are composed of Pb and Sn. Pb Sn elements do not well-distributed. The determi- nation results of different grains and same grains in different point region by electron probe show that the content ratios are quite different. The analysis with a transmission lens (probe) proves that when some -points are determi- ned on one scale, the content of Sn is 100%，the content Of Pb is approxi- mately 100%. Based on all above, the researched minerals still do pot form a new pha- se. They are only ultramicro mixtures of native lead and native tin. The for- mation of the mixture is due to the exsolution of lead-tin solid solution. The exsolution proceeds when the high temperature of lead-tin solid solution drops to 183℃.