Sturdy Marble

Found in the nearby tunnel, go left when you can to find it.

Found behind a horizontal aerosol can below the hanging donut, inside Toxic Anthill: South Entrance.

Found behind an aerosol above a rat skull, inside Toxic Anthill.

In a large cavern inside the Toxic Anthill.

In a cavern on the south side of the Toxic Anthill.

Located in the tunnel. Blow up the cracked wall to the right at the first intersection, and follow the path behind. The node will be against the wall at the bottom of the path, left of the Raw Science.

Located next to the wall.

Found deep underground in the tunnels of the Spider Den Anthill.

Found deep underground in the Spider Den Anthill, in the cavern with the suspended stones.

In the underground tunnel, accessible via the entrance behind the Dead Root.

In the tunnel accessible via the space under the amp.

Found underneath the Terrarium.