A new Sr-Ti hydrous silicate mineral was found in albitite cutting serpentinite at Ohmi, Niigata Prefecture, central Japan. It occurs as aggregate of fibrous crystals of light pink in color. The mineral is monoclinic with a=10.958 Å; b=7.778 Å; c=7.799 Å, β=100°54′, space group P2₁/m. Crystals are elongated along b-axis, density 3.38; hardness 3.5, weak pleochroism, α=1.849, γ=1.715. Chemical analysis gave SiO₂ 34.79, Ti₂O₃ 10.27, Fe₂O₃ 0.20, SrO 47.37, H₂O 6.68, Total 99.31. The chemical formulae of the mineral is Sr₃TiSi₄O₁₂(OH)•2H₂O.