Sylvinite is a sedimentary rock made of a mechanical mixture of the minerals sylvite (KCl, or potassium chloride) and halite (NaCl, or sodium chloride). [1] [2] Sylvinite is the most important source for the production of potash in North America, Russia and the UK. [2] [3] Most Canadian operations mine sylvinite with proportions of approximately 31% KCl and 66% NaCl with the balance being insoluble clays, anhydrite and in some locations carnallite. Other deposits of sylvinite are located in Belarus, Brazil, France, Germany, Kazakhstan, Slovakia and Spain. [4]