The mining world is a special place that you can go to to mine freely, without having to worry about ruining terrain. Occasionally the world gets regenerated (and everything in the mining world is lost), giving the world fresh terrain and resources. (Regenerations will be announced at least a week before.)
Important notice: Do not start a quarry closer than 200 blocks to the wasteland portal while in the wasteland! This is very important as anyone not respecting this rule could create a large amount of lag for the players entering the mining world. If you want, you can place blocks/signs to indicate where the 200 blocks limit starts.
Visiting the World
You can get to the Wastland mining world, by typing /spawn
Once there you should see a portal made of gem blocks. This is the entrance.
Getting back is easy. While you're in the mining world, just type /spawn
What You'll Find
While the mining world is just "a regular old world," it will be more abundant in resources generally. On Wasteland, you will be able to find ores more easily and quarry more tracks of land.
The world is temporary, so don't build anything too permanent. This world no longer exists on the server