Tuff and volcanic breccia are both composed of a variety of igneous fragments. Their classification as either felsic, intermediate, or mafic therefore depends on the particular:

A) mineral content of each individual unit.
B) average grain size of each individual unit.
C) thickness of each individual unit.

Felsic

Refers to igneous rocks that are rich in lighter elements such as silicon and oxygen, generally characterized by light colors.

Mafic

A material having high contents of magnesium (Mg) and iron (Fe), generally accompanied by a decreased amount of silica.

Igneous Fragments

Pieces of rock formed from the cooling and solidification of magma or lava, often found in volcanic or plutonic environments.