Fire Sunder

Motes only stack to ten. If you want to carry around more than ten you have to waste more bag slots them. By combining the motes into primals you can store 110 motes in the space you used to only be able to keep 20 since you can stack primals. When you need more motes, just shatter a primal. This is actually a nice little bag space saver for miners.

A few recipes require the use of motes of fire, rather than a full primal fire. This spell allows a miner to drop the primal into motes, and use them in another recipe. It also means that if motes sell better than primals for some reason, the miner can break one down for a bit of extra money.

Useful recipes that require only motes of fire as opposed to whole primal fires:

http://www.wowhead.com/?item=22574#reagent-for

Any miner will normally be happy to sunder a few primals for you if you ask nice. Some may charge a small fee: most will probably just ask to pinch a few motes for themselves.