Is plaster a homogeneous mixture or heterogeneous mixture explain?

Plaster is neither a homogeneous nor heterogeneous mixture. Plaster (gypsum) is a compound, Plaster of Paris / Calcium Sulfate or also called Gypsum is composed of calcium sulphate (CaSO4) and water (H2O). Its chemical name is calcium sulphate dihydrate (CaSO4. 2H2O).