Post-magma is a geological term used to describe the solidified LAVA that has cooled and hardened after an eruption. It is also known as volcanic rock, and is composed of minerals such as quartz, feldspar, and mica. Post-magma is formed when magma, molten rock from deep within the Earth's crust, is forced to the surface through volcanic activity. The term post-magma is used to distinguish it from magma, which is still in its molten state.