Basalt is an extrusive igneous rock formed from the rapid cooling of lava. It is mafic, meaning it is relatively rich in magnesium and iron, which gives it a dark color.

Here are some key characteristics of basalt:

* Composition: Primarily composed of plagioclase feldspar, pyroxene, and olivine, with lesser amounts of other minerals like quartz and amphibole.

* Texture: Typically fine-grained, meaning the mineral crystals are too small to see with the naked eye.

* Color: Dark gray to black, often with a greenish or brownish hue.

* Formation: Formed when molten lava erupts from volcanoes and cools quickly on the Earth's surface.

* Occurrence: Very common, making up a significant portion of the Earth's crust, particularly in oceanic plates.

Key points to remember about basalt:

* It is a common rock type found in many places around the world.

* It is relatively dense and strong, making it suitable for various construction and landscaping applications.

* It is often associated with volcanic activity and can be found in areas with active volcanoes.

Basalt is a fascinating and important rock type that plays a significant role in the Earth's geology and evolution.