Is it true that sulphide and carbonate ores of zinc are heated to convert into their oxides to extract the metal?

• The given statement is true.
• The metals are found in the earth’s crust mainly as oxides, sulphides or carbonates. 
• The metals can be extracted easily from their oxide as compared to their sulphides and carbonates. So, the metal sulphides and metal carbonates must be converted into metal oxide, before extracting metals from their respective ores. 
•  Roasting is the process of converting sulphide ores into their oxides by heating strongly and in the presence of excess air. 

             $\mathrm{ZnS} + 3{\mathrm{O}}_2\stackrel{\mathrm{heat}}{\to } 2\mathrm{ZnO} + 2{\mathrm{SO}}_2$

• Calcination is the conversion of carbonate ores into their oxides by heating strongly in limited air in the presence of suitable reducing agents such as carbon.

              ${\mathrm{ZnCO}}_3 \stackrel{\mathrm{heat}}{\to } \mathrm{ZnO} + {\mathrm{CO}}_2$