Solution
All minerals are ores, but not all minerals are ores because some of them may contain significant amounts of undesirable materials like sand, stones, and earthly impurities. For instance: Clay and bauxite, two minerals that contain aluminium, are found in the crust of the earth. Only bauxite can be used to efficiently and profitably extract aluminium from these. Thus, it follows that bauxite is an aluminium ore. On the other hand, there hasn’t been a simple or inexpensive way to extract aluminium from clay. Thus, clay ceases to be an ore of aluminium and is now only a mineral.