From the Super Mario Wiki
Statue Leaves are rare items found in Super Mario 3D Land (only in Special Worlds). When Mario or Luigi grabs a Statue Leaf, he resembles his Tanooki form, but wears a scarf of his corresponding color, and gains the ability to transform into a statue instead of doing a Ground Pound, thus avoiding enemies (which cannot hurt him) and hazards.
This power-up first appears in Special 1-1 in Super Mario 3D Land, and is relatively common in the Special Worlds of the game, replacing the Super Leaf. It is also similar to the Tanooki Suit from Super Mario Bros. 3, but it doesn't give flight.
Statue Leaves are grayish Super Leaves with alternating bright and dark stripes. They also look as if they are made out of stone, which makes sense, since they give the statue ability.
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