Q.List the important sources of sulphur.

Step 1 — Elemental (native) sulphur.

Large underground deposits of free sulphur occur (historically Sicily; large deposits in USA, Mexico), extracted using the Frasch process (superheated water/air/steam pumped down to melt and force sulphur to the surface).

Step 2 — Sulphide ores.

Sulphur occurs combined with metals as sulphide minerals: galena (PbS), zinc blende (ZnS), copper pyrites ($CuFeS_2$), iron pyrites ($FeS_2$) — important both as sulphur sources and as metal ores.

Step 3 — Sulphate minerals.

Sulphur also occurs as sulphate minerals: gypsum ($CaSO_4\cdot2H_2O$), Epsom salt ($MgSO_4\cdot7H_2O$), and baryte ($BaSO_4$).

Step 4 — Combined/organic sources. …

Categorise sources systematically into elemental deposits, sulphide ores, sulphate minerals, and organic/gas-associated combined forms — the s …

• Don't list only elemental sulphur — the question expects the full range of sources (ores, minerals, organic matter), not just native deposits. …