Portal Frame Stone

Information
The Portal Frame Stone is one of the "hard to break" blocks in the game. It can be crafted using an Ancient Gem, Rock, a Bucket of Lava (you'll keep the bucket not the lava), and Black Crystal. To make an Underworld Portal, place it in a hollow 4 blocks wide and 5 blocks tall. Then fill the hollow part with Transfer Blocks. In Version 1.0, Portal Frame Stone lost its function.

To see more blocks like this one, go to this page --> Blocks