This question already has an answer here:
Obligatory Backstory*: In year, whatever the count is now, humans get their black hole ships in working order, and decide to venture into space. We colonize a few worlds, and start establishing some loose connections with other races (think sort of Native American v.s. Europeans, except not necessarily a power difference). Cruising along, we find material X. Material X is very valuable. We see a race, which roughly would be pronounced as numahs in human vocal cords, are hogging it up (numahs are at approximately the same level of development as us, although might use a different system of propulsion). Our military leaders try and negotiate to get some of it, but then they up and decide to slaughter our women and children for no reason besides hating us (and well, the women and children were on the ship that started the battle, but still)! Obviously, numahs don't deserve material X. We will get material X, and they will get none.
End Obligatory Backstory
So humans have always fought over resources, and I don't think we'll stop in space. My question is, what would space faring civilizations fight over? I had a couple ideas, but they don't quite pan out.
- Worm Holes: They don't actually exist.
- Micro Black Holes: Some what hard to harvest, Doubtful to occur naturally, Not too hard to make
- Antimatter: Doubtful to occur naturally, Hard to harvest
- Neutron Stars: Hard to harvest, why would you want it
- Gold: My favorite so far, Gold could be rare in space too
What other materials could space civilizations fight over. Include both the material, how to harvest it, and why we would fight over it. If you have any reason why the above would be a better idea than I originally thought, feel free to include it.
*Not obligatory for reading, feel free to skip