Warded Stone blocks are added by Thaumcraft, possibly with SMP in mind. They are essentially blocks that remember who placed them - and they are (nearly) unbreakable by anyone but that player.
When paired with Arcane Doors, a player is able to construct a fort that is (almost) impervious to outside interference - including other players! Meaning that they can only be broken by the player who placed them or a player/admin in creative mode.
They are (almost*) literally indestructable to anyone but the player who placed them. Even IC2 Nukes cannot destroy these blocks - when a set of 9 nukes was detonated inside a chamber composed of one-block-thick walls of Warded Stone, no terrain was damaged at all. They will not absorb the radiation effect, however, so bear this in mind.
Other players have been known to encase your impervious base with their own impervious blocks, preventing you from leaving your base. The Portable Hole is NOT able to tunnel through these blocks.
It also seems that you can't place Warded Stone with a Wand of Equal Trade, the game mechanics considering it as something/one else, and not you, placing the stone. (I'll have to test that part later. -Kerydwenn
"These stone blocks are almost unbreakable to anyone except the person who placed them. What is more, they are highly resistant to explosions.
They come in a variety of colours to please even the most fashion conscious thaumaturge."
|Warded Stone and Door|
The image to the right demonstrates the recipe (note, obscured in the image is the cost of 10 Vis). To get any manner of color, simply substitute the color you wish to achieve in where the bonemeal would go.
Possibly a bug, but Red Power block breakers are able to dislodge them as if they were normal blocks, while pistons cannot budge them. This is however fixed in later versions.
On mindcrack pack V8.3.2 Redpower block breakers do not break warded stone, nor do Computercraft's mining turtle and the Buildcraft quarries don't destroy them either but dig 3 blocks under them, and then stop, but continue digging around the warded stone, the quarry will also refuse to start if you place warded stone in its building phase. Gravitation Suite's Vajra cannot break them, but if you right click a white warded stone it spews out a white warded stone and turns the original block invisible.