Here's a breakdown of the composition:
* Minerals: Basalt is primarily composed of silicate minerals, with the most common being:
* Plagioclase feldspar: A light-colored mineral that gives basalt a light gray to black color.
* Pyroxene: A dark green to black mineral that gives basalt its characteristic dark color.
* Olivine: A green to yellow mineral that can be present in some basalts.
* Other Components: While silicate minerals dominate, basalt can also contain small amounts of other minerals like:
* Magnetite: A black magnetic mineral.
* Ilmenite: A black mineral.
* Apatite: A phosphate mineral.
The specific mineral composition of basalt can vary slightly depending on the source of the magma, but it generally has a low silica content and is relatively rich in iron and magnesium.
Formation:
Basalt forms when magma rises from the Earth's mantle and erupts at the surface as lava. This lava cools and solidifies quickly, often forming characteristic features like:
* Lava flows: Large, relatively flat sheets of solidified lava.
* Pillow lavas: Rounded, pillow-shaped masses of lava that form underwater.
Basalt is a very common rock type, especially found in oceanic crust and at volcanic regions.