The World Anchor is a special block added by RailCraft that keeps chunks loaded when a player is not in-game or otherwise in that chunk or dimension. The world anchor works in both multiplayer and singleplayer.
The World Anchor keeps a 3-by-3 chunk area (9 total chunks) centered around the anchor active at all times that the anchor is in place. Pressing the Show Chunk loader particles (default F9 key) will show particles in the area under the effect by the Anchor. The particles appear purple, similar to the Enderman warp particles and the particles that float outside of a Nether Portal.
World Anchors are commonly used to keep machines active while the player is offline (Only in Multiplayer) or in another dimension. Use of a World Anchor with the Blast Furnace or Coke Oven is common, due to the large amount of time it takes to produce items with these devices.
Using several world anchors in a Single Player world can cause a lot of lag on machines with lower end specs. Use of world anchors in multiplayer is similar to having a player connected 24/7, so low-end servers should avoid their use to avoid the lag associated World Anchor utilization.
Occasionally the Show particles function will not work in multiplayer. This is due to the particles being client side effects.
Contrary to being made of Obsidian, an Iron or better pickaxe can be used to collect. It can also be retrieved by use of a Crowbar.
Chunks kept loaded by a World Anchor will not be saved to disk when the player leaves the area or logs off of a multiplayer server, which can lead to data loss if the server is shutdown improperly. Removing the World Anchor(s), logging off and then logging back in to place them again will ensure the chunks are saved. This also effects the contents of any chests in the loaded area, but not the player's inventory.