Rock-crushing scrimshaw

The Rock-crushing scrimshaw is an item that can be made with the Fletching skill at level 85 once all four scroll fragments of Rock Crushing have been retrieved from the Player-owned port.

When equipped, it offers a 15% chance to crush the ore (losing it in the process) in exchange for increased experience while Mining.

The crushed ore appears to give 38% bonus experience, which means 15% chance to give 38% bonus experience. This works out at about 5.7% bonus experience.

This effect does work when mining rocks in the Living Rock Cavern.