Small crystals.
EXPLANATION:
Extrusive igneous rocks are formed when the magma reaches the Earth's surface and most of the extrusive (volcanic) rocks have very small crystals.
The examples of the Extrusive rocks include rhyolite, basalt, obsidian, and andesite.
These rocks emit on the surfaces where they form the small crystals. These rocks are used in building construction and statues.
Igneous rocks are very unique because of their mineral and chemical substances.
