The precious furnace is the first specialty furnace that we developed. It is used in mining to smelt metal from ore stones. Current theory is that it picks up a secondary material in the smelt - use 1-6 clusters of what you want, with the rest dirt/sand. See the discussion on the furnace results page.
Vital statistics:
Built: in a compound, uses 5x8 cells
Skill/Tech required: Metallurgy