A modular fireplace construction utilizes interlocking corner joints in the fire block area to provide a stable, free-standing base for the smoke chamber and chimney sections above. Individual sections are cast from an extremely heat resistant composition containing Luminate cement and Perlite aggregate. The completed fireplace does not require the addition of a flue liner. Dowel apertures may be formed in the individual sections which receive handling dowels to enable assemblers to easily lift and accurately place the sections during assembly.