The correct answer is option 1: Calcium. Plaster of Paris is a white powdery substance that is commonly used for making casts and molds. It is made by heating gypsum, a mineral composed of calcium sulfate dihydrate. When gypsum is heated, it loses its water content and becomes calcium sulfate hemihydrate, which is the main component of Plaster of Paris.

Calcium is a metal that is commonly found in nature and is essential for various biological processes. It is abundant in rocks, minerals, and the Earth`s crust. In the case of Plaster of Paris, calcium is present in the form of calcium sulfate hemihydrate. This compound is mixed with water to form a paste, which can then be manipulated and shaped before hardening into a solid material.

It is important to note that while calcium is the metal found in Plaster of Paris, it is not typically referred to as a metal in this context. Calcium is more commonly recognized as an essential mineral for human health and is found in foods like milk, cheese, and leafy greens.