The word is RETORT. At least that's what I found when I Googled mercury and gold.
According to Merriam-Webster the definition of RETORT is: a vessel or chamber in which substances are distilled or decomposed by heat
Good news - I found a new spot to dig.
Bad news - the new stuff that's showing up in my cons. Lots of pyrite (a real pain in the... to pan) and mercury. A nice little nugget showed up in my sluice covered in the stuff (mercury). Also, many little balls of the stuff with each pan.
Finding all sorts of designs for retorts I figured it was fairly simple in principle and "should be" easy to fabricate. So, I built myself one.
My problem was not knowing what the heck I was doing. I ended up frying my nice little nugget instead of just burning off the mercury.
Lesson learned - too much heat will easily trash things.
Good news is the retort works!