Hello! You need to make changes in two files: Recipes_Mining.xml & Buildings_Mines.xml.
It is also important that the name of the resource you need coincides with how it is called not in the game, but in the files. The error is hidden somewhere here.

so what changes do i ahve to make exactly, this is my first time wirting xml code and i dont knw up from down

Don't know if this still help in time. A notepad++ is advisable to used for the editing.

Here are the Recipes_Mining.xml & Buildings_Mines.xml file location. (The steam library is not exactly the same for everyone, if you do not know where it is, you can search on Youtube to see where to locate it.)

G:\SteamLibrary\steamapps\workshop\content\294100\1545681321\Defs\RecipeDefs\Recipes_Mining.xml

G:\SteamLibrary\steamapps\workshop\content\294100\1545681321\Defs\ThingDefs_Buildings\Buildings_Mines.xml






1. In Recipes_Mining.xml, copy and paste the below code above or below the original one.

<RecipeDef ParentName="MiningWork">
<defName>Excavate_ Steel </defName>
<label>mining Steel </label>
<description>mining Steel .</description>
<jobString>Mining Steel .</jobString>
<!--
Steel is worth 1.37 silver/unit
1.37 x 332 ticks/silver = 455 ticks
-->
<workAmount>655</workAmount>
<products>
< Steel >10< /Steel >
</products>
</RecipeDef>

Then edit all the "Steel" to the item you want, for example, I used copper from Project RimFactory - Materials. (Steel -> copper)

<RecipeDef ParentName="MiningWork">
<defName>Excavate_copper</defName>
<label>mining copper</label>
<description>mining copper.</description>
<jobString>Mining copper.</jobString>
<!--
copper is worth 1.37 silver/unit
1.37 x 332 ticks/silver = 455 ticks
-->
<workAmount>555</workAmount>
<products>
<PRF_Copper>10</PRF_Copper>
</products>
</RecipeDef>

You should pay attention from the below phrase

<products>
<PRF_Copper>10</PRF_Copper>
</products>

the PRF_Copper is the ore ID from the ProjectFactory - Materials mod, you should find this ID from that mod folder and scrool through all .xml file to find it.







2. As for Buildings_Mines.xml, it will be simple. Just copy the below and paste it above or below the code again.

<li>Excavate_Steel</li>

Then edit the <li>Excavate_Steel</li> to what you typed in Recipes_Mining.xml. The example from below is copy from the above example.

<li>Excavate_copper</li>

3. Once you have edited all the variable, click save in notepad++, and try it out in the game.
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4. If you could not get the result of of your expectation, JUST LET IT GO!!!

You don't want to waste 1 day just to get the code work correctly. Trust me, it's not worth it. Play 1 day rim world is much better then wasting a day to get half-cheated ore from coding Rimworld mod.
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5. Hope you all stay safe in 2021.

@ThirySeven
How would you add Sky steel?