Most geology students know what a basalt or gabbro is, but occasionally even introductory texts will refer to different mafic rocks and ultramafic rocks. This list very briefly describes a few of these, just enough to differentiate between them based on composition and formation.
Mafic & ultramafic rocks
Metamorphic rocks, minerals, grade, and facies
Metamorphic rocks form when a preexisting rock (protolith) is transformed into a different rock due to pressure, heat, or chemical alteration. Tectonics and burial can supply pressure and heat on a wide scale (regional metamorphism), while igneous intrusions can bake adjacent rocks (contact metamorphism). Hydrothermal fluids power chemical alteration. This page has useful diagrams of metamorphic processes, while this one has good notes, and this one has both! Read more →
Most common elements and oxides in rock-forming minerals
After the Big Bang, the universe was made up of the two lightest elements: hydrogen and some helium. Nucleosynthesis was responsible for creating heavier elements; young stars form helium out of hydrogen.
In the later stages of a massive star's life, helium is converted into heavier elements like carbon, oxygen, silicon, and iron. When a star goes supernova, they create elements heavier than iron. Elements with even atomic numbers are an order of magnitude more common than odd ones. Read more →