Leviathan Scales

Leviathan Scales are a key item from Final Fantasy VII.

They are located in the Junon Underwater Reactor, in the chest on the far left in front of the user controlled Submarine.

They are used in the Cave in Wutai on Da Chao. If you climb Da Chao and enter the cave, the flames that block your path react with the scales, dousing them.

This leads the path to the Steal as Well materia.