Here's why:

* Amphibolite is a metamorphic rock primarily composed of amphibole minerals, such as hornblende.

* Basalt and gabbro are igneous rocks that are rich in calcium, magnesium, and iron. These elements are the building blocks for amphibole minerals.

* When basalt or gabbro is subjected to heat and pressure during metamorphism, the original minerals transform into amphiboles, forming amphibolite.

Other rocks that can metamorphose into amphibolite include:

* Mafic volcanic rocks (like andesite)

* Some sedimentary rocks (like graywacke)

It's important to remember that the specific parent rock of any given amphibolite can vary, and its composition can provide clues about the original rock and the metamorphic conditions it experienced.