What is 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 called?

polyhalite — 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. (Webster's 1913.)

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