Question #5ded8
1 Answer
The size of crystals in igneous rocks depend on where and how fast the rocks cool.
Explanation:
Igneous rocks that form slowly under the surface (in the crust) have large crystals such as granite that can have large crystals of quartz, feldspar and biotite as part of the granite. These are known as intrusive rocks.
Rocks like basalt that are erupted onto Earth's surface like in Hawaii, have very small grains due to crystallising in open air. Because the rock broke the surface, it would be known as a extrusive rock.
Igneous rocks like obsidian are glassy because they have been quenched, this means they have cooled very very rapidly. This occurs when the lava/magma makes contact with something much cooler than it, like water or other cooler rocks. The rock hasn't had time to crystallised and all the atoms are frozen in a random state.
