Forsterite
Forsterite is the magnesium-rich form of olivine, common in chondrules and the oldest dust of the Solar System.
Forsterite is the magnesium end of the olivine family, with the formula Mg2SiO4. Olivine is a solid solution, meaning iron and magnesium can swap places freely in the crystal, and pure forsterite is the version with almost no iron. It is pale, often colourless or light green, and melts at a very high temperature, about 1,890 °C.
Because it is so heat-resistant, forsterite was one of the first silicate minerals to condense from the hot gas around the infant Sun. It is abundant in the chondrules of primitive carbonaceous chondrites, in amoeboid olivine aggregates, and in comet dust collected by the Stardust mission.
Scientists describe olivine by its forsterite or fayalite percentage. An olivine written Fo90, for example, has 90 per cent of the magnesium end member. Ordinary chondrites contain olivine with roughly 68 to 84 per cent forsterite, depending on the group, which is one way H, L and LL chondrites are told apart.
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