The present invention provides a geopolymeric cement formed from a precursor having a relatively high alumina content (Si:Al atomic ratio of less than or equal to 1.3:1) to form an alkaline multiphase alumino-silicate material.The precursor comprises basaltic rock in which kaolinization is at an advanced stage, preferably Interbasaltic material found in Northern Ireland.The present invention also provides structural units for constructing a building, the structural units being manufactured using the geopolymeric cement of the invention.The invention also provides a process for producing a geopolymeric cement comprising a precursor having a relatively high alumina content (Si:Al atomic ratio of less than or equal to 1.3:1) to form an alkaline alumino-silicate geopolymer material for manufacturing geopolymeric structural building units having compressive strengths of greater than 3 N/mm2 and preferably having compressive strengths in the range of 12-25 N/mm2.