More specifically, oceanic plates are composed of a rock type called basalt, which is a dark-colored, fine-grained igneous rock. Basalt is rich in silicate minerals, such as:

* Pyroxene

* Olivine

* Plagioclase feldspar

These silicate minerals are characterized by their tetrahedral structure, where a silicon atom is bonded to four oxygen atoms. This structure gives silicate minerals their unique properties and makes them abundant in the Earth's crust.