Is our Earth an oddity in space?

When you think of the rocks that make up our home planet (but also all the other rocky planets in the solar system), you probably immediately think of the fact that olivine and orthopyroxene are the predominant minerals in the Earth’s mantle. If not, you are probably not a geologist. I confess, I didn’t know that either. But is this actually normal? Are all rocky planets in the universe composed primarily of these minerals? That’s an important question, because other rock types absorb more water...