terra alba: finely pulverized gypsum used especially as a pigment
gypsum: a common white or colorless mineral (hydrated calcium sulphate) used to make cements and plasters (especially plaster of Paris)
corpuscular radiation: a stream of atomic or subatomic particles that may be charged positively (e.g. alpha particles) or negatively (e.g. beta particles) or not at all (e.g. neutrons)