[karisma]

What happens if you attempt to recover CaCO3 by adding 3M H2SO4 instead of 3M HCI to a Si)2/CaCO3 residue?

[Tetrahedrite]

You won't be able to recover CaCO3? using sulfuric acid because firstly, carbonate is lost as CO2 when acid is added, and, secondly, if you are trying to dissolve the CaCO3 with sulfuric you will have trouble because CaSO4 (anhydrite or gypsum) is fairly insoluble where as CaCl2 is much more soluble.
What is the experiment you are doing?