The most common inorganic flame retardants are the hydroxides or aluminium and magnesium. Aluminium trihydroxide (ATH) is by far the most widely used flame retardant. It is very inexpensive, but usually requires higher loadings in polymers of up to more than 65%. Its mode of action  is based on the release of water  (Endothermic process) which cools the polymer and dilutes the flame zone. Magnesium hydroxide (MDH) is used in polymers which have higher processing temperatures, because it is stable up to temperatures of around 310 °C versus ATH which decomposes around 210 °C.

Aluminum hydroxide flame retardants (white powder) for processing temperatures up to about 210° C, for wire and cable, electronic and electrical components based on thermoset resins, building materials, mass transportation, paints and varnishes, paper and plaster with organic binder.

Magnesium hydroxide flame retardants (white powder) for processing temperatures up to about 310° C for wire and cable, electronic and electrical components based on polyamide resins, building materials.

There are other minerals that  show flame retarding effects and are used in commercial applications. Most of them are used as synergists i.e. they enhance the performance of other flame retardants or they are used for specific effects like the suppression of smoke formation, increasing char formation etc. For example, borates are used as mixtures of boric acids and borax as flame retardants for cellulose (cotton) and of zinc borate for PVC and other plastics like polyolefins, elastomers, polyamides, or epoxy resins. In halogen-containing systems, zinc borate is used in conjunction with antimony oxide (mainly to reduce cost), while in halogen-free systems it is normally used in conjunction with ATH, MDH or red phosphorus.

In some particular applications zinc borate can be used alone. Boron containing compounds act by stepwise release of water and formation of a glassy coating which protects the surface.

Zinc compounds were initially developed as smoke suppressants for PVC (Zinc hydroxystannate). Later it was found that they also act as flame retardants in certain plastics mainly by promoting char formation.

Other inorganic fillers like talcum or chalk (calcium carbonate) are sometimes called flame retardants, their mode of action is simply by dilution, i.e. they they reduce the amount of polymer and hence the fire load.