Iron Nodes are sometimes visible in the walls/floors/ceilings of underground caves (which often also contain lakes of healing Mineral Water), but can best be discovered by digging mineshafts yourself which requires Obsidian Mining Cells as an equipment (or better Power Cells).
Iron Ore cannot be pulled from Nodes, instead Extractors of any kind have to be placed:
- Basic Extractors will extract 3 Iron Ore from 1 Iron Node within 5 minutes
- Advanced Extractors will extract 6 Iron Ore from 1 Iron Node in 2:30 minutes
- Super Extractors will extract 9 Iron Ore from 1 Iron Node in 1:30 minutes
Currently Nodes themselves cannot be pulled/taken nor placed (August 2016).
For explanations about template worlds go to the official forums:http://steamcommunity.com/sharedfiles/filedetails/?id=634088783
Additionally to extracting Ore from Iron Nodes, you can also find Iron Ore occasionally in Iron Treasure Chests on the Lava layer a bit deeper underground and/or in Diamond Treasure Chests on the Corruption layer deep down.
These chests will also spawn on artificial biomes built of rocks from these underground-layers on the surface in complete darkness (either at night or when roofs and walls are added too).
Super Excavators are needed to remove rocks that the Stalactite layer is made of, however they require rather rare materials to be crafted and from deeper layers too. Currently there is no Excavator that can remove Lava layer-blocks or corrupted blocks.