Disclosed is a randomly moldable thermosetting paste containing small mineral balls, an inorganic binder or a mixture of such binders, and a fiber moiety. Said paste is characterized in that hollow mineral microballs are used. The paste which cures starting at room temperature is suitable for use as a fire-resistant and heat-insulating material that is provided with great inherent stability in the cured state. The inventive paste is suitable for the production of inexpensive low-density molded parts. Moreover, the invention makes it possible to dispense with the use of organic solvents such that the paste can be used directly by the user.