Here's why:

* Composition: Felsic rocks are rich in silica (SiO₂) and contain high amounts of feldspar and quartz. These minerals are relatively light.

* Minerals: The specific density of the minerals within a felsic rock influences its overall density.

* Porosity: The presence of pores and air spaces within the rock can lower its density.

It's important to note that the density of felsic rocks can vary depending on the specific mineral composition and the presence of other factors like porosity. However, the general range of 2.6 to 2.7 g/cm³ is a good starting point.