Basalt
Basalt (UK: / ˈ b æ s. ɔː l t,əl t /; US: / b ə ˈ s ɔː l t, ˈ b eɪ ˌ s ɔː l t /) is an aphanitic extrusive igneous rock formed from the rapid cooling of lowviscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or than 90% of all volcanic rock on Earth is basalt. Rapidcooling, finegrained basalt is chemically ...