debug block

Second internal replacement slot for procedural decorations. Like the other debug placeholders, it is meant to be consumed by structure logic, not used as an ordinary block in survival or creative building.

Rock formations use this slot for their main stone body, which is why it appears far more often than replace_1 inside ore-bearing rocks. The same slot also shows up as the second replacement entry in simple decorations and as the base material marker for several ambiguous monuments.