The most important class of rock-forming minerals on Earth are the silicates.

Here's why:

* Abundance: Silicates make up over 90% of Earth's crust and mantle. They are incredibly common.

* Variety: Silicates come in a huge variety of forms, with different compositions and structures, leading to a diverse range of rock types.

* Foundation of Geology: Understanding silicates is fundamental to understanding the formation, composition, and evolution of rocks and the Earth itself.

While other mineral classes are important (like carbonates, oxides, and sulfides), none are as prevalent or influential as silicates in Earth's geology.