Sylvanite was formed at the late mineralization stage of the Beiling gold deposit and occurs in comby network quartz, associated with native gold. The mineral assemblage includes sylvanite-na tive tellurium-altaite-native gold-quartz and sylvanite-melonite-altaite-quartz. Native tellurium,melonite and altaite exist as inclusions in sylvanite. Sylvanite occurs in columnar, tabular and grained forms and assume polysynthetic twin with strong anisotropy and bireflectance.Hv50=216—219 kg/mm2. Chemical composition:Ag 10.58%—12.36%,Au 23.70%—24.51%, Te 61.67%—62.30%, with small amounts of As,Cu, Zn, Fe and Ni. Chemical formula is Ag Au1.0494—1.2691Te4.215—4.9182. The strongest X-ray diffraction lines are 3.054(85),2.153(31),and 1.984(18). Unit cell parameters:a0=8.9502°A,b0=4.4973°A,c0=14.7063°A andβ=145°58′. The ore deposit was formed at 115.2—161.8℃and lower sulfur fugacity. Hydrogen and oxygen isotopic studies show that ore-forming fluids came from meteoric water of low salinity.The gold deposit is considered to be of volcanic epithermal type.