From Pikipedia, the Pikmin wiki
The Mirrored Element (レアメタルS?, lit.: "Rare Metal S") is a treasure in Pikmin 2. It is actually a silver Morgan dollar coin. It is found in the fourth sublevel in the Dream Den, which is crawling with Armored Cannon Beetle Larvae and Anode Beetles. The Cannon Beetles can be manipulated to eliminate other Beetles and enemies. The treasure may be near a gas pipe or some Anode Beetles.
“Talking to the boss makes me crave the power to order people around. He just sits on his haunch all day, barking out wildly irrational requests. Arrgg... When will it be my turn to be the boss?”
“All reason flies in the face of this sparkle. It's not flashy, but it still inspires avarice!”
Names in other languages