I was playing on a world that my friend was hosting, and I found a duplication glitch. I went to pick up a beacon, and he picked it up while I was still in the menu. I then spammed the pickup button a few times because the menu wasn't closing. I then manually close the menu and check my inventory. To both of our surprise, I had picked up eight beacons from the one beacon. This may work with all things that can be picked up such as portable miners.