Final answer:
Cryolite is not an ore of iron; it is used in aluminum production. Hematite and magnetite, however, are both iron ores.
Step-by-step explanation:
b) Cryolite. Cryolite is not an ore of iron (Fe). Instead, it is a mineral that contains aluminum and is used in the extraction of aluminum from its ore, bauxite. The other options, haematite and magnetite, are indeed ores of iron. Haematite (also spelled hematite) and magnetite are both iron oxides, with haematite having the chemical formula Fe2O3, and magnetite having the formula Fe3O4. These minerals are significant sources of iron for industrial processes, including the production of iron and steel. In contrast, cryolite plays a role in the aluminum extraction process due to its ability to lower the melting point of aluminum oxide during electrolysis.