Cinnabar (HgS) is an ore of mercury.
when Cinnabar, HgS is heated in air, it is first converted into HgO, HgO is then reduced to Hg on further heating.
Cinnabar (HgS) is an ore of Mercury.
The metals being less reactive can be obtained by reducing their oxides to metals by heating alone.
So, when Cinnabar is heated in air, it first changes into its oxide and then into mercury metal.