Building Materials - Engineering

Q1:

Basalt is

A sedimentary rock

B metamorphic rock

C extrusive igneous rock

D intrusive igneous rock.

ANS:C - extrusive igneous rock

Basalt is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill. It has a composition similar to gabbro. Extrusive igneous rocks form when magma reaches the Earth's surface a volcano and cools quickly.
Most extrusive (volcanic) rocks have small crystals. Examples include basalt, rhyolite, andesite, and obsidian. Basalt is an intrusive igneous rock because it found in shallow depth inside the earth. And Granite is intrusive igneous rock.