PURPOSE: To obtain a hydraulic inorganic composition excellent in impact strength and flexural strength and suitable for member for building by adding a synthetic fiber to a composition consisting essentially of a hydraulic inorganic substance, fine powder quartzite having a specific weight-average diameter and a mineral fiber.

CONSTITUTION: This inorganic composition is obtained by adding 0.1-20 pts.wt. of a synthetic fiber to 100 pts.wt. of solid content of a composition consisting essentially of a hydraulic inorganic substance, fine powder quartzite having 0.5-10μ weight average particle diameter and a mineral fiber. The hydraulic inorganic substance used includes ordinary portland cement, high-early-strength portland cement, alumina cement or blast furnace cement. A fine powder quartzite pulverized to 0.5-10μ weight-average particle diameter is used as the fine powder quartzite. The hydraulic inorganic composition is subjected to dehydrating press molding and cured to provide the objective the hydraulic inorganic molding.