igneous clusters are formed by conditions heat / viruses
heat_of_formation is heat. specific_heat is multi_dimensional_quantity. groundmass is igneous_rock. rift_valley_fever_virus is bunyaviridae_virus. rift_valley_fever_virus is viral_agent. rubella_virus is rna_virus. rna_virus is virus. mumps_virus is rna_virus. bunyaviridae_virus is rna_virus.