"Periodite" is not a recognized term in geology or mineralogy. It's likely a misspelling of "peridotite."

Peridotite is a igneous rock composed primarily of olivine and pyroxene minerals.

Here's the breakdown:

* Rock: A naturally occurring solid aggregate of one or more minerals.

* Mineral: A naturally occurring, solid, inorganic substance with a definite chemical composition and a characteristic crystalline structure.

Therefore, peridotite is a rock, not a mineral.