Nagastone is the main block that makes up the wall surrounding the Naga Courtyard. It has about the same minability of a normal stone brick. They can (and probably will) be broken by the Naga, so don't try to use them for protection.
Decoration[]
Nagastone has an interesting behavior. If placed next to another Nagastone it will position the block to make a snake. The Naga head brick is not required, but is obtainable the same way you get the nagastone.