Here are a new chemworks and iron ore mine released as city buildings. See my previous post if you want to learn how they work. If you want to just use them:
To build a scenario:
Copy the contents of the "BUILD" folder into your ObjData folder.
Build the scenario using these buildings. They are set to produce 24 units of cargo per month, per building (ie: 1x1 and 2x2 buildings produce the same amount).
To play a scenario:
When you've finished building, copy the contents of the "PLAY" folder into your ObjData folder. Now your new industries should produce cargo (chem or iron ore) and not be destroyed, unless the AI interferes.
Here's the "proof of concept"

Screenshots of a custom city building Chemical Works, and surviving ~20 years of metropolitan growth:
Cheers,
Bryan