Iron Ore is a fairly-common type of Terrain Special - specifically one of the Minerals. It appears as group of rust-red streaks on the overland map, and is found on Hill and Mountain tiles by default. It is somewhat more common on Arcanus than on Myrror.
If the Iron Ore tile is within the catchment area of a Town, the Construction Cost of most Normal Units in that town will be 5% less than their default cost. Several Iron Ore tiles, as well as Coal tiles, can together reduce this to a minimum of 50% of each unit's default cost.
The bonuses from Iron Ore are doubled if the town has a Miners' Guild. Iron Ore can be changed into Gold Ore using the Transmute spell, and Gold Ore can be changed into Iron Ore using the same method. Iron Ore can be removed from a tile by raising a Volcano in that tile. Corruption temporarily removes the bonus that Iron Ore gives to nearby towns.
Much of the technology of warfare is based on the ability to construct fine weapons and armor from materials that are both sturdy (do not break easily) and malleable (easy to shape). Iron, a fairly common material, has long proven to be useful for these purposes. Although it is not as strong as Mithril or Adamantium, it is far more abundant.
In order to shape Iron into weapons and armor, it is first necessary to mine Iron Ore out of the ground. In some places, veins of Iron Ore appear on the surface, but most commonly they'll be found deep under hills or mountains. An especially-rich vein of Iron Ore can be extracted more efficiently - in large quantities - thus enabling large-scale production of weapons made from this material.
In the game, Iron Ore appears as a group of rust-red streaks across the tile's surface. It is easier to spot Iron Ore on Arcanus because it stands out against the white mountains and green hills, but on Myrror it can blend into the brown terrain easily.
Initial Placement and Terrain Edit
Iron Ore tiles are fairly common compared to other Minerals - at least on the plane of Arcanus, where where they are often found in Hilly terrain. On Myrror it is one of the less-common minerals, and may actually be rarer than Mithril Ore or even Adamantium Ore. Note that due to the random nature of world-generation, it is quite possible (though unlikely) that no Iron Ore will appear on either Plane at all!
The only way to remove an Iron Ore mineral is to raise a new Volcano underneath it. This permanently removes Iron Ore from the tile - and it cannot be restored. Volcanoes can be created using either the Raise Volcano or Armageddon spells.
Mineral Effects Edit
Iron Ore is a Mineral, and thus provides a bonus to nearby towns.
When a Iron Ore tile is within the catchment area of a Town, the Construction Cost of most new Normal Units produced in that town is reduced by 5% of its original cost. This allows slightly-faster production of new units here.
Unit Cost Reduction Edit
With several Iron Ore and/or Coal tiles in a town's catchment area, the bonuses from these Minerals will stack together, reducing unit construction costs even further. For example, the presence of three Iron Ore tiles near a town gives -15% on each unit's Construction Cost. The maximum possible bonus is -50% - i.e. each unit costs half as much as it normally would.
Note that some units require neither weapons nor armor, so production of these units is not made cheaper by Iron Ore or Coal. These are the Shamans, Priests, Magicians, Warlocks, Triremes, Galleys and Warships. Their costs are not affected in any way.
When selecting a Normal Unit for construction, you can see its actual cost compared to its default cost. This is displayed at the top of the information panel, with two numbers. The number in parentheses is the original cost of the unit. The other number is the unit's actual cost.
It is possible to build two towns close enough together that their catchment areas overlap. Shared tiles are marked by a red "1/2" label, seen in each town's details screen.
When an Iron Ore mineral occupies a shared tile, it will give half of its benefit to each town. Therefore, production of Normal Units each town will cost only -2.5% less than normal, instead of -5%.
Note that it is quite possible for this state to change during play, as new towns are established and existing towns are destroyed. The Iron Ore tile's bonuses will be redistributed automatically in such events.
Miners' Guild Bonus Edit
When a Miners' Guild is erected in a town that has access to Iron Ore, each Iron Ore tile's effect is doubled.
Therefore, a single Iron Ore tile will reduce the Construction Cost of Normal Units by 10% rather than just 5%. Remember that the maximum reduction is always 50% (when accounting for all Iron Ore and Coal tiles in a town's vicinity).
A Iron Ore tile that's shared between two towns (see above) will therefore generate its default bonus (-5% cost reduction) for whichever town has a Miners' Guild. If both towns have a Miners' Guild, they both enjoy the tile's default bonus (-5% each).
This is done in order to increase Gold output at the expense of unit-production speed. It can be useful for a number of reasons - particularly when the empire is running low on Gold to support all of its existing units.
Remember that transmutation is not permanent: you can always cast the spell a second time to change Gold Ore back into Iron Ore.
The Corruption spell can be cast on a tile containing Iron Ore. In such an event, both the Iron Ore itself as well as the tile it's on will cease providing any bonuses to nearby towns.
To combat this, send Shamans or Priests to Purify the affected tile immediately. If several tiles are Corrupted, Iron Ore tiles are usually the lowest priority for Purification. Several spells, including Gaia's Blessing and Consecration, may also help if they are available.