The ore that contains the metal in the form of fluoride is:

Concept:

The following are the chemical formulas of the given compounds:

Magnetite - FE₃O₄ (Oxide of Iron)

Sphalerite - ZnS (Ore of Zinc)

Cryolite - Na₃AlF₆ (Sodium Hexafluoroaluminate)

Malachite - CuCO₃.Cu(OH)₂ (Copper Carbonate Hydroxide mineral)

Ore is a naturally occurring solid material from which a metal or valuable mineral can be extracted profitably.

Cryolite is the ore that contains the metal in the form of fluoride.

It was used as an ore of aluminium and later in the electrolytic processing of the aluminium-rich oxide ore bauxite (itself a combination of aluminium oxide minerals such as gibbsite, boehmite and diaspore).

The difficulty of separating aluminium from oxygen in the oxide ores was overcome by the use of cryolite as a flux to dissolve the oxide mineral(s).

Pure cryolite itself melts at 1012°C (1285 K), and it can dissolve the aluminium oxides sufficiently well to allow easy extraction of the aluminium by electrolysis.

Substantial energy is still needed for both heating the materials and the electrolysis, but it is much more energy-efficient than melting the oxides themselves. As natural cryolite is too rare to be used for this purpose, synthetic sodium aluminium fluoride is produced from the common mineral fluorite.