Specifically, it's a pyroclastic rock, which means it's formed from the accumulation and consolidation of fragments of volcanic material ejected during an explosive eruption. These fragments can include ash, pumice, and larger rock blocks.

Here's a breakdown:

* Igneous: Formed from the cooling and solidification of magma or lava.

* Pyroclastic: Formed from volcanic debris.

* Tuff: Specifically formed from the accumulation of fine-grained volcanic ash and pumice.

Tuff can be further classified based on the composition of the volcanic fragments and the degree of welding (compaction) that has occurred.