A ceramics particle produced by a flame fusion method, containing MgO and SiO2 as main components, and having a MgO/SiO2 weight ratio of from 1.0:1 to 1.45:1, and an average particle size of from 0.001 to 1.5 mm; a spherical molding sand containing MgO and SiO2 as main components, and having a MgO/SiO2 weight ratio of from 1.0:1 to 1.45:1, and an average particle size of from 0.001 to 1.5 mm, produced by a flame fusion method; a spherical molding sand, comprising MgO and SiO2 as main components, and having a MgO/SiO2 weight ratio of from 1.0:1 to 1.45:1, an average particle size of from 0.001 to 1.5 mm, and a spherical degree of 0.95 or more; a process for producing the above spherical molding sand; a casting mold containing the spherical molding sand as defined above; and a casting produced by casting with the mold as defined above.