Extraction Alt.

[HydroMan]

Ability: Extraction
Alternative/Addon: First off all, the ability itself would need to be changed into earthbending ability, meaning that with metalbending disabled earthbenders would be able to bind it which you'll see the reason why. Shifting on a coal ore will make all the remaining coal inside that block drop out, turning the block to stone afterwards. You would then be able to pick up the remain drop ore that you extracted. With metalbending enabled, the bender would be able to extract iron normally and coal, but while disabled only coal is possible to extract.
Canon: Proof of coalbending to exist

Earth compression: It is possible for earthbenders to compress large chunks of rock into smaller, denser chunks, or to compress several smaller chunks into one big piece of rock. Haru and his father, Tyro, used this technique, compressing several small pieces of coal into one big coal boulder. The fact that two earthbenders were required to perform it suggests that this technique is quite difficult.

Earth material manipulation: Earthbending is not limited to rock or soil alone. An earthbender can also manipulate coal, gems, crystals, and other earth-based materials, like meteorites and jennamite.[5]

- Quote from the avatar wiki.​

 

[Moonelight]

Placing this Looking Into, I can agree with this.