cinnabar

 cinnabar was the main ingredient of the pigment vermillion, which was very toxic and deadly to humans as it has high contents of mercury and sulphur.

Here is what the mineral looked like before it got ground down into a powder to produce vermillion.

The main components of cinnabar was mercury and sulphur and when put together they create a highly toxic substance called mercury sufide.

Here is a visual representation of mercury and sulphur one is a liquid and the other is a rock.

when put together they create cinnabar