Chemistry : Unknown green powder become black solid upon heating.?

Question

What are the unknown chemicals. This is under Qualitative Analysis.

Answer 1

At a guess, copper(II) carbonate loses carbon dioxide to become copper(II) oxide.

Answer 2

One reaction that comes to mind is the conversion of green manganese ( II ) oxide to manganese ( IV) oxide when the monoxide is heated in air

     2MnO( green )  + O2 -------  2 MnO2 ( brownish black )

as stated earlier by another it may be a CuCO3 ---- CuO + CO2 as well  Without knowing other details it is hard to say