Star Piece

Hidden, in small grey rock outside cave entrance

Possible reward for solving Treasure Tom's riddle (daily)

Snow Zone

Daily, Reward from the Challenge Rock quest

Hidden, in small rock in southwestern corner (B2F)

Hidden in small rock west of NPC Ace Trainer Stella (B2F)

(5F)

Behind Strength rock, southwestern corner (Cave)

Behind Strength rock, northern side (Cave)

Far lower right corner (right of NPC Battle Girl Chan) (Room 2)

Southern part of elevated area (After BW2)

Hidden, in tree ontop of cliff above river, right side where there seems to be one tree missing in the continuous line of trees.

Ontop cliff above river, left side

In maze-like ruin below PokéCenter. Right side, near exit leading behind ledge