Phosphates & Oxides
Iron Oxide
What it is
Minerals made of iron and oxygen. Hematite is the most important iron ore and the mineral that makes Mars red. Magnetite is naturally magnetic — lodestone (naturally magnetized magnetite) was humanity's first compass.
How it forms
Hematite forms in sedimentary banded iron formations, weathering zones, and hydrothermal veins. Magnetite crystallizes from iron-rich magmas and in metamorphic rocks.
Fe₂O₃ (Hematite) / Fe₃O₄ (Magnetite)
