Igneous rocks close igneous rockIgneous rocks are ... As the magma cools, mineral crystals will begin to grow. These crystals will grow and interlock to form a hard crystalline rock.

Igneous rocks are formed when magma underground or ... sometimes plant or animal material, and also crystals left behind when ...

Like other igneous rocks, the glossy glass originates from ... Because of the lack of crystals in the overall structure, pure obsidian takes on a smooth, glossy shine. However, snowflake patterns ...