(a) Baryte, (b) Galena, (c) Zinc blende and (d) Copper pyrites. How many of these minerals are sulphide based? ______

We need to identify which of the given minerals are sulphide-based.

(a) Baryte: The chemical formula of baryte is $$BaSO_4$$ (barium sulphate). This is a sulphate mineral, not a sulphide mineral.

(b) Galena: The chemical formula of galena is $$PbS$$ (lead sulphide). This is a sulphide mineral.

(c) Zinc blende: The chemical formula of zinc blende is $$ZnS$$ (zinc sulphide). This is a sulphide mineral.

(d) Copper pyrites: The chemical formula of copper pyrites is $$CuFeS_2$$ (copper iron sulphide). This is a sulphide mineral.

Therefore, among the four minerals, 3 are sulphide-based (galena, zinc blende, and copper pyrites).