We don't have synonyms for polyhalite yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are polyhaline and polybasite.
(n) :
(mineralogy) A mineral usually occurring in fibrous masses, of a brick-red color, being tinged with iron, and consisting chiefly of the sulphates of lime, magnesia, and soda.
(n) :
(mineralogy) A mineral usually occurring in fibrous masses, of a brick-red color, being tinged with iron, and consisting chiefly of the sulphates of lime, magnesia, and soda.