Moonstone

The moonstone, is one of a couple of stones, that can help to evolve specific Pokémon.

Pokémon that could evolve with a moonstone

 * Nidorina to  Nidoqueen
 * Nidorino to  Nidoking
 * Clefairy to  Clefable
 * Jigglypuff to  Wigglytuff
 * Skitty to  Delcatty
 * Munna to  Musharna

Belonging

 * Red-Green-Blue Arc
 * Red found one in at Mt. Moon.