Here's why:

* Basalt's Composition: Basalt is a mafic igneous rock, meaning it's rich in magnesium and iron. This composition leads to the presence of specific minerals.

* Plagioclase Feldspar: This is a common mineral in igneous rocks, and in basalt, it's typically the most abundant mineral. It forms a significant part of the rock's overall composition.

* Other Minerals: While basalt does contain other minerals like pyroxene, olivine, and sometimes quartz, plagioclase feldspar is the dominant one.

Let me know if you'd like to know more about the specific types of plagioclase feldspar in basalt!