Gem-finding scrimshaw

The Gem-finding scrimshaw is an item that can be made with the Fletching skill at level 90 once all four scroll fragments of Gem Finding have been retrieved from the Player-owned port, requiring 10 Ancient bones. When this item is made you receive 4200 Fletching experience. Boosts and assists cannot be used to make any scrimshaws.

The only requirement is level 80 mining. When equipped, it offers a very low chance of finding high-level uncut gems, namely as uncut diamond, uncut dragonstone or uncut onyx, when successfully Mining an ore. It does not impact the chance of finding low-level gems such as sapphires, emeralds or rubies. High level rocks have a greater chance to yield these, though. It doesn't work with shooting stars, the lava flow mine, seren stones, concentrated coal, concentrated gold or red sandstone. It lasts 3 hours before degrading into nothing.

Chances
Gems extracted as a result of the scrimshaw are acquired simultaneously while extracting an ore from a rock (the ore and gem appear in inventory together), whereas usually gems are obtained instead of extracting an ore from a rock. It is possible to find 2 gems in the same rock.