Eulytite is an extremely rare bismuth silicate mineral. The natural eulytite reported in this paper is attached on the geodes or cracks of tremoilite fibers produced in the Chaobuleng skarn-type iron-polymetallic deposit in Dong Ujimqin Banner of Inner Mongolia. The eulytite commonly has the forms of tetrahedron {111} and trigonal tristetrahedron, crystal size of 0.07～0.15 mm, transparent light yellow color, glass luster, brittleness and colorless streak. Its Vickers microhardness is 487～583 kg/mm² (near 5 on the Mohs hardness scale), its calculated density and N are 7.11 g/cm³ and 2.15 respectively, and its mineral chemical formula is Bi₄Si₃O₁₂. The strongest reflections in the X-ray powder diffraction pattern [d(Å)(I)] are 4.26 (85), 3.29 (100), 2.77(79), 2.11(45) and 1.67(33), and the unit cell parameters are a=10.116(2) Å, V=1 035.2(7) ų,and Z=4. The genesis of eulytite is also discussed in this paper.