Here's how it works:

* Starting Material: Hematite (Fe₂O₃) often forms from the oxidation of other iron-containing minerals, like magnetite (Fe₃O₄) or iron sulfides (like pyrite, FeS₂).

* Oxidation: Oxygen (O₂) reacts with the iron in these minerals, causing the iron to lose electrons and become oxidized (Fe²⁺ to Fe³⁺).

* Hematite Formation: This oxidation process leads to the formation of hematite, where iron is in its +3 oxidation state.

Example:

Magnetite (Fe₃O₄) can be oxidized to hematite (Fe₂O₃) through the following reaction:

2 Fe₃O₄ + O₂ → 3 Fe₂O₃

Important Note: Oxidation of iron-containing minerals to form hematite is a common geological process that occurs in various environments, including:

* Weathering: Exposure to air and water can oxidize iron-containing minerals, forming hematite as a reddish-brown stain.

* Hydrothermal Activity: Hot, mineral-rich fluids can react with iron-bearing rocks, leading to the formation of hematite deposits.

* Metamorphism: High temperatures and pressures during metamorphism can cause the oxidation of iron minerals, resulting in the formation of hematite.