This is Cinnibar, mercury ore. Put some in a sealed jar in the Sun. When it heats up a bit it gives off mercury vapor that condenses on the inside of the jar. Bingo, metallic mercury.
An outcropping of Cinnibar looks like somebody got a can of dark red spray paint ("oxblood") and sprayed it on the ground.
I believe you can simply cook it. Yeah, in a retort to catch the vapors.
But, that is what slaves are for.