Suessite

Suessite is an isotropic mineral, Isotropism is defined as an optical property of a mineral that stays the same from whatever direction it is observed. In thin-section microscopy, an isotropic mineral has only one refractive index. This means that light that passes through the mineral is not split into two different directions, but it passes through unchanged. Suessite, as determined from the previous definition, only has one index of refraction. When Keil, Fuchs, and Berkley first discovered the mineral they described it as having a relatively low optical relief, but there was no determination of the index of refraction. In plane polarized light, suessite is a reddish-brown color that shows no pleochroism.

"Suessite can form under highly reducing conditions" say the scientists who discovered this mineral. Only one out of eight ureilites studied (the North Haig ureilite) by this group contained suessite. Most contained trace amounts of kamacite which is the mineral from which Suessite is formed. In this particular study, the meteorite that contained suessite contained the highest amounts of shock metamorphism, which can be determined from the size of a shatter cone created from the impact. This could mean that suessite is formed due to the extreme increase in temperature combined with reduction of silicate rims, shortly followed by a rapid decrease in temperature. This means that, in meteorites, the abundance of suessite can be used to identify deformation associated with shock metamorphism, which could be used to determine various characteristics of the studied meteorites.

The other natural iron silicides include gupeiite (Fe₃Si), hapkeite (Fe₂Si), linzhiite (FeSi₂), luobusaite (Fe_0.84Si₂), naquite (FeSi), xifengite (Fe₅Si₃), and zangboite (TiFeSi₂).