Sylvinite

 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.[3][4] Most Canadian operations mine sylvinite with proportions of about 31% KCl and 66% NaCl with the balance being insoluble clays, anhydrite and in some locations carnallite. Other deposits of sylvinite are in Belarus, Brazil, France, Germany, Kazakhstan, Slovakia and Spain.[5]

Sylvinite from Perm Krai, Russia
Close-up view of sylvinite from Perm, Russia

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 Metasyntactic variable, which is released under the 
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