Here's why:

* Compounds are formed when two or more elements chemically combine in a fixed ratio. For example, water (H₂O) is a compound because it always has two hydrogen atoms and one oxygen atom.

* Mixtures are combinations of two or more substances that are not chemically bonded. The substances in a mixture retain their individual properties.

Ores are naturally occurring rocks that contain valuable minerals. They are mixtures of different minerals, often with the valuable mineral embedded within a matrix of other minerals.

For example, iron ore is a mixture of iron oxides like hematite (Fe₂O₃) and magnetite (Fe₃O₄) along with other minerals like quartz and clay. The iron oxides are the valuable minerals, while the other minerals are impurities.

Key takeaway: Ores are mixtures because they consist of different substances that are not chemically bonded together.