Fe2Mg2Si4O12OH2

Fe2Mg2Si4O12OH2, also known as ferroan monticellite, is a mineral belonging to the olivine group. It is a magnesium-iron silicate with the chemical formula Fe2Mg2Si4O12(OH)2. This mineral is typically found in metamorphic rocks, particularly those that have undergone high-pressure, low-temperature metamorphism. It is characterized by its dark green to brown color and its prismatic or tabular crystal habit. Ferroan monticellite is an important indicator mineral in metamorphic petrology, as it provides insights into the pressure and temperature conditions under which the rocks formed. Its presence is often associated with the presence of other minerals such as garnet, kyanite, and staurolite, which are also indicative of high-pressure metamorphism. The mineral's name is derived from its composition, with "ferroan" indicating the presence of iron, "monticellite" referring to its structural similarity to the mineral monticellite (Mg2Si4O10), and "OH2" indicating the presence of hydroxyl groups in its structure.