| http://www.w3.org/ns/prov#value | - The salt there mined contains, besides the chlorides and sulphates of sodium, magnesium, calcium and other salts, considerable quantities of potassium chloride, and the Stassfurt mines at present are practically the entire source of all potassium compounds, in spite of the fact that other localities have been sought to produce these compounds on a commercial basis, especially by the United States
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