Star Piecein Pokémon Polished Crystal

A hunk of red gem. Sell very high. Star Piece is more valuable than Stardust and one of the better sellable items in the game. It's essentially a money pickup. Wild Staryu and Starmie can hold Star Pieces, so if you're farming money, catching those can be profitable. Otherwise, sell any you find since they have no battle or evolution use.