Which oxide is generally not associated with hematite (Fe2O3) iron ore as a natural constituent or common gangue impurity?

Introduction / Context:
Hematite iron ore primarily contains iron(III) oxide with various gangue minerals. Understanding typical impurities helps in beneficiation route selection and slag design in ironmaking.

Given Data / Assumptions:

• Common gangue: silica, alumina, phosphorus/sulfur-bearing species.
• Minor oxides may be present depending on deposit.

Concept / Approach:
Titanium oxide and manganese oxide can occur as trace impurities; calcium oxide appears from carbonate gangue (e.g., calcite/dolomite) or flux addition, though not intrinsic to the hematite lattice. Cobalt oxide is not a typical component or common impurity associated with iron ore bodies on an appreciable level.

Step-by-Step Solution:
List likely impurities from geology: TiO2, MnO, SiO2, Al2O3, carbonates.Note that CoO occurrence is rare/negligible in iron ores.Select cobalt oxide as “not present.”

Verification / Alternative check:
Typical assay tables of hematite ores seldom record cobalt oxides; processing does not account for cobalt removal in iron ore circuits.

Why Other Options Are Wrong:
TiO2/MnO: observed in some ores.CaO: may occur via carbonates or be considered in gangue/flux context.SiO2: classic gangue mineral.

Common Pitfalls:
Assuming any listed oxide cannot occur; geology varies, but CoO is distinctly uncommon.

Final Answer:
Cobalt oxide