The Gold Ghost in the Across the Chasm mission can be accessed by heading down into the old mine. Progress through the entire mine until you come to the large wheel located in the finale room, used for mining. Use the 5000 the make the wheel spin and spit out rocks onto the the conveyor belt (the third rock will be large and golden).

After the golden rock disappears into the warp point, head back up the elevator and into the room with the fire (and the tea pot). Carry the golden rock over to the fire to melt it, flushing out this pretty well hidden Gold Ghost.