Were was the Nostromo coming from

I just finished seeing Alien last night for about the 50th time. I do think that there could be questions answered about Prometheous if you paid good attention at Alien. One question about Alien has always bugged me. We know that the Nostromo was transporting ore back to earth. But from where? This planet or planetoid were the ore is mined has to be father from earth then LV-426. Remember the ship was deviated from the original destination which was earth to LV-426.  Maybe the ore they were transporting came from LV-223. This is just me throwing a question out there. But maybe after what took place on LV-223. The Weyland-Yutani group sent another team of explorers out to investigate what happened on LV-223, and landed on the other side of the planet. They told the Weyland-Yutani heads that the only thing they found was ore. So they then the company decided to make LV-223 a mining facility. Thats just my guess.