"Shieldite" is not a recognized mineral or geological term. It is possible that you are referring to a fictional substance or a misspelling of a real mineral.

Could you please provide more context or clarify what you are looking for? Perhaps you meant:

* "Shale": A type of sedimentary rock that is mined in many locations around the world.

* "Siderite": An iron carbonate mineral that is mined for iron ore.

* A fictional mineral: If you are referring to a mineral from a book, movie, or game, please let me know the source.

Once I have more information, I can help you find the answer you are looking for.