I is for Igneous rock #atozchallenge,

What is igneous rock?
Igneous rock is one of the three main types of rock. The word igneous comes from the Latin word for fire. When magma or lava cools it becomes igneous rock. Magma comes from the earth's center. It can be seen on the surface as lava near active volcanoes such as in Volcano National Park on the big island of Hawaii.
The significance of igneous rocks are the following:
The composition of igneous rock give data about the Earth's mantle.
Their absolute age can be determined from dating methods
Their features can yield data about plate tectonics.
They contain important mineral deposits.