Here's a breakdown:
Felsic:
* High silica content (60-75% SiO2).
* Rich in lighter elements like potassium (K), sodium (Na), and aluminum (Al).
* Typically light in color, ranging from white to pink.
* Common minerals include quartz, feldspar, and mica.
* Examples: Granite, rhyolite, obsidian.
* Often found in continental settings and associated with explosive volcanic eruptions.
Mafic:
* Lower silica content (45-55% SiO2).
* Rich in heavier elements like magnesium (Mg) and iron (Fe).
* Darker in color, ranging from dark gray to black.
* Common minerals include pyroxene, olivine, and plagioclase feldspar.
* Examples: Basalt, gabbro, peridotite.
* Often found in oceanic settings and associated with effusive volcanic eruptions.
Ultramafic:
* Even lower silica content than mafic rocks (<45% SiO2).
* Very rich in magnesium and iron.
* Very dark in color, almost black.
* Common minerals include olivine and pyroxene.
* Examples: Peridotite, dunite.
* Found in the Earth's mantle and rarely exposed at the surface.
Understanding the terms:
* Felsic comes from the first letters of feldspar and silica.
* Mafic comes from magnesium and ferric iron.
The terms "felsic" and "mafic" are fundamental to understanding the formation, characteristics, and properties of igneous rocks. They are also used to classify other geological materials, like magma and lava.
