A hydrogel liquid precursor includes an inorganic mineral and a monomer, wherein the inorganic mineral accounts for 15 percent by mass or more of the hydrogel liquid precursor, wherein the hydrogel liquid precursor has an initial viscosity of 20 mPa·s or less at 25 degrees C., and wherein the hydrogel liquid precursor has a ratio of a two-week viscosity to the initial viscosity of from 0.90 to 1.10, the two-week viscosity representing a viscosity of the hydrogel liquid precursor at 25 degrees C. after being left at 50 degrees C. for two weeks.