Ores are generally included as part of a mother rock called the gangue. Mechanical crushing and milling break the rock down into fine powders where the individual ore particles are separate from, but still tightly mixed with, the surrounding minerals. Flotation is one of the methods used to separate the crushed ores from the gangue.
Flotation, or froth flotation, in a chemical/mechanical separation process used mainly in the mining industry. Its basis of operation is to selectively separate hydrophobic materials from hydrophilic ones using air bubbles injected into a slurry holding finely ground ores. Additives added to the mix make the desired ore particles 'stick' to the bubbles and float on top of the slurry, while the non desirable mineral particles from the gangue sink to the bottom. The separated ores attached to the bubbles are skimmed off for further processing.
Additives can act as collectors, frothers and modifiers.
The flotation process is used for the separation of a large range of sulfides, carbonates and oxides prior to further refinement.
The collected ores are called the concentrate, while the separated gangue is the tailings.
Flotation is largely an experimental science, which requires adaptations for every mine and separation plant. Flotation on Mars should work as on the Earth, although the lower gravity might have some influence and the availability of various additives might be limited. Flotation is effective for sulfates, and as sulfur is abundant on Mars, sulfated minerals may be common.