Suessite is a rare iron silicide mineral with chemical formula: Fe₃Si. The mineral was named after Professor

Hans E. Suess Hans Eduard Suess (December 16, 1909 – September 20, 1993) was an Austrian born American physical chemist and nuclear physicist. He was a grandson of the Austrian geologist Eduard Suess. Career Suess earned his Ph.D. in chemistry from the ...

. It was discovered in 1982 during the chemical analysis of The North Haig

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

pigeonite

achondrite An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystall ...

( ureilite). It is a cream white color in reflected light, and ranges in size from 1 μm "blebs" to elongated grains that can reach up to 0.45 cm in length. This mineral belongs in the isometric crystal class. The isometric class has crystallographic axes that are all the same length and each of the three axes

perpendicular In elementary geometry, two geometric objects are perpendicular if they intersect at a right angle (90 degrees or π/2 radians). The condition of perpendicularity may be represented graphically using the ''perpendicular symbol'', ⟂. It can ...

to the other two. It is isotropic, has a structural type of DO3 and a crystal lattice of BiF₃.

Optical Properties

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 In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

. 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 Pleochroism (from Greek πλέων, ''pléōn'', "more" and χρῶμα, ''khrôma'', "color") is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light. Backgrou ...

Importance of suessite

"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 Kamacite is an alloy of iron and nickel, which is found on Earth only in meteorites. According to the International Mineralogical Association (IMA) it is considered a proper nickel-rich variety of the mineral native iron. The proportion iron:ni ...

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.

Other iron silicide minerals

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

xifengite Xifengite ( Fe5 Si3) is a rare metallic iron silicide mineral. The crystal system of xifengite is hexagonal. It has a specific gravity of 6.45 and a Mohs hardness of 5.5. It occurs as steel gray inclusions within other meteorite derived nick ...

(Fe₅Si₃), and zangboite (TiFeSi₂).Mindat, http://www.mindat.org

References

{{Authority control Native element minerals Iron minerals Ferromagnetic materials Transition metal silicides Magnetic minerals Cubic minerals Minerals in space group 229