Liquid lava or magma cools and solidifies to create primary rocks, commonly referred to as igneous rocks. Based on their mineral makeup and formation environment, intrusive (plutonic) and extrusive (volcanic) rocks are the two basic categories into which they are divided.

Large crystals can form in intrusive igneous rocks, which are formed when slowly cooling magma solidifies beneath the Earth’s surface. Typical kinds include of:

Granite: A light-colored stone with a high silica concentration that also includes feldspar and quartz.
Diorite: A mixture of light and dark minerals having an intermediate hue and composition.
Gabbro: Dark-colored, high in iron and magnesium, and frequently including pyroxene and plagioclase.

Smaller crystals are produced as lava cools rapidly on the Earth’s surface, giving rise to extrusive igneous rocks. Typical kinds include of:

Basalt: Usually formed from quickly cooling lava, basalt is dark, finely grained, and rich in iron and magnesium.
Rhyolite: Fine-grained granite with a high silica concentration and a light hue.
Andesite: Usually found in volcanic arcs, andesite has an intermediate hue and composition.

Both kinds add to the diversity of Earth’s geology and are essential to the rock cycle.