Deposit
Deposits are areas of the world where natural resources can be found and mined. There are five resources that can be found in deposits: stone, coal, clay, ore, gems and sithilon ore. Each deposit can only be mined by a corresponding, matching type of mine built over them. And even though different mines need to be used, they all function exactly the same.
When starting a new game, the player will be able to see the percentage of deposits in a chosen area. It is wise to try to choose an area with every type of deposit, or at the very least, as many as possible and/or the most important and frequently used ones, such as stone and coal. Each deposit has a different level of how frequent they will appear in a world. Gem deposits are rare, while sithilon ore deposits are even rarer.
Placing mines
Mines are placed like any other building. When placing a mine on a matching deposit, the player must click and drag an area over a deposit. Mines must encompass both deposit and non-deposit ones. The reason for this is while the mines must be obviously placed over deposits the player wants to mine, there must be extra space for the mine's components, being the required storage and auxiliaries (which speed up production).
As one would expect, at least one tile of a matching deposit must be encompassed in the selection box for the mine's placement to be valid. Though mines have their own storage, they must eventually be moved to a warehouse or export depot (if the player wishes to trade away the resource). If a mine's storage is full, production will cease. Though not required, it is advised to build a warehouse near a mine if any other existing one is too far away. This is to ensure that citizens won't have to walk too far away just to store a mine's contents.
During the early stages of a game, getting the most out of your mines can be tricky. This is because the player will most likely not have any metal when starting out, yet metal is needed to build the auxiliaries of a mine, boosting its efficiency and production speed. This can be rectified in two ways: simply building an ore mine without auxiliaries, then (slowly) mining as much ore as possible and smelting it, then later using the smelted ore/metal to build auxiliaries, and the second way is to simply trade for metal.