Vivianite, named after the English mineralogist F. G. Vivian, is a rare mineral of secondary origin, associated with pyrite in copper and tin veins. It forms as a weathering product from primary iron- manganese phosphates in pegmatites, and is a hydrous phosphate of iron of a blue to green colour, growing darker on Exposure to the air. It occurs in monoclinic crystals, also fibrous, massive, and earthy. It is also found in beds of clay and has a relative hardness of 3.
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