Here's a breakdown:
* Xeno means "foreign" or "strange" in Greek.
* Lith means "stone" in Greek.
So, a xenolith is literally a "foreign stone" within another rock.
How they form:
Xenoliths form when magma or lava rises through the Earth's crust and incorporates pieces of the surrounding rock into its flow. These "foreign" rock fragments are then baked and hardened within the newly forming igneous rock.
Examples:
* A piece of limestone within a granite intrusion.
* A fragment of basalt within a rhyolite flow.
Xenoliths are important to geologists because they provide insights into the composition and structure of the Earth's crust and mantle.
