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Which minerals are important sources of potassium compounds?

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A periodic table element box for potassium shows atomic number 19, symbol K, atomic weight 39.0983, electron configuration [Ar]4s1, and name potassium. Icons indicate it is an alkali metal, solid at room temperature, body-centered cubic crystal structure, and has strongly basic higher-valence oxides. A key explains the symbols for alkali metals, solid state, body-centered cubic structure, and strong basicity. — potassium Properties of potassium.

Important sources of potassium compounds are primarily obtained from water-soluble minerals found in ancient lake beds and seabeds. These minerals, often collectively referred to as potash, include:1

Sylvite: The chief source of potassium, consisting of potassium chloride (KCl).21
Carnallite: A hydrous potassium magnesium chloride ( $K M g C l_{3} \cdot 6 H_{2} O$ ).1
Polyhalite: A complex sulfate mineral ( $K_{2} C a_{2} M g [S O_{4}]_{4} \cdot 2 H_{2} O$ ).1
Langbeinite: A potassium magnesium sulfate ( $K_{2} M g_{2} [S O_{4}]_{3}$ ).1
Kainite: A natural salt consisting of a hydrous sulfate and chloride of magnesium and potassium ( $K M g (S O_{4}) C l \cdot 3 H_{2} O$ ).3

While potassium is abundant in Earth's crust, it is also present in insoluble silicate minerals such as muscovite and orthoclase feldspar. However, because these are insoluble in water, they are difficult to process and are not the primary sources for commercial potassium compounds. Researchers are currently exploring these silicate minerals as potential slow-release fertilizers to improve soil health.14