Magnesite

Magnesite is the mineral, which is processed into many magnesium containing products. It can be used for the production of fertilizers, as a binder material, e.g. in flooring material (so called Magnesite screed), as mineral flame retardant and smoke suppressant in plastics, as catalyst, filler and reinforcing agent in the production of synthetic rubber (e.g. neoprene), in cosmetics and in the preparation of magnesium chemicals. 

High purity grades can also be used as food additive (e.g. prevents table salt from clumping together) which is known as E504.