How ultramafic similar to felsic

The similarity between some of the 2 terms mentioned is explained in the following section of the description.

Explanation:

In comparison to mafic rocks, which have been comparatively stronger in iron as well as magnesium, the resemblances between felsic but instead ultramafic rocks become close. Felsic corresponds to mineral deposits, magma, including rocks of silicate that are supplemented with smaller lighter particles including silicon, magnesium, gold, sodium, or potassium. Felsic magma as well as lava seems to be stronger than mafic lava throughout viscosity.