Do you ever find yourself with a horde of useless gold and precious gems.
Do you also ever get bored of pouring precious wood Into your furnace to get coal so you can keep smelting your stacks and stacks of ore.
Well boy do I have the solution for you.
Once you've found the trader and reached the iron age purchase yourself a thunderstone and construct an obliterator.
Head back to the friendly trader and swap your stacks of gold for as much squirmy worm bait as you can fit in your pockets.
Go back over to your obliterator. Squidge all the worms in, flick the lever and let Thor work his magic.
Every 100 worms will give you 25 coal. If 100 worms are worth 10 gold then you can effectively get 5 coal for every 2 gold.
I shan't be needing to burn my precious wood any time soon. Murdering worms is where it's at.