Plain Stone

is one of the six ores that players can collect in the world of TERA. It is used for Smelting.

is found by mining a Node. Mining a node will give players between 3-5. can also be acquired by chance when mining other ore nodes.

Titan's Ember, Titan's Ease, Titan's Truce, and Titan's Temper can also be acquired by chance when mining a Node.

Source
This ore can be found in almost all areas of the world. It is not limited to a certain region like other ores.