Fe₃(SiFe)O₅(OH)₄

This sample of cronstedtite is displayed in the Smithsonian Museum of Natural History. Cronstedtite is a silicate mineral with the composition Fe₃(SiFe)O₅(OH)₄. The sample at left is about 12 cm across and is from Herja, Crisana-Maramures, Romania. This sample is described as cronstedtite with siderite.