So basically what I want to have as an output is the sum of areas of the surfaces of particles.
"Specific surface area (SSA) is a property of solids defined as the total surface area of a material per unit of mass, (with units of m²/kg or m²/g) or solid or bulk volume (units of m²/m³ or m−1). It is a derived scientific value that can be used to determine the type and properties of a material (e.g. soil or snow)"
Hope its better explained now.