Comment by pavel_lishin

> These kinds of McGuffins lean towards physics are different in other parts of the galaxy/universe if there are minerals found only in certain parts of the galaxy.

Or the local conditions are such that they produce different chemical compounds.

I'm not going to strike gold in my backyard, but people in Colorado might. There's not a lot of diamond production happening within reach underneath my location, but there's plenty in parts of Africa.

If we want to take it to space, there's not a lot of Helium-3 to be easily extracted on Earth, but apparently there's quite a bit more on the Moon.