From the Super Mario Wiki
Statue Leaves are items only found in Super Mario 3D Land. When Mario or Luigi grabs a Statue Leaf, he becomes his Tanooki form, but wears a scarf of his corresponding color, and regains the ability to transform into a statue instead of doing a Ground Pound, thus avoiding enemies (which cannot hurt him) and hazards. This makes it similar to the Tanooki Suit from Super Mario Bros. 3, but it doesn't give flight.
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.
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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