Suessite is a rare iron

silicide A silicide is a type of chemical compound that combines silicon and a (usually) more electropositive element. Silicon is more electropositive than carbon. Silicides are structurally closer to borides than to carbides. Similar to borides and carb ...

mineral with chemical formula: Fe₃Si. The mineral was named after Professor Hans E. Suess. 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 quickl ...

pigeonite Pigeonite is a mineral in the clinopyroxene subgroup of the pyroxene group. It has a general formula of . The calcium cation fraction can vary from 5% to 25%, with iron and magnesium making up the rest of the cations. Pigeonite crystallizes in th ...

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 recrystalli ...

(

ureilite Ureilite is a rare type of stony meteorite that has a unique mineralogical composition very different from that of other stony meteorites. This dark grey or brownish meteorite type is named after the village Novy Urey ( Cyrillic: ''Новый У ...

). 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 ca ...

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. 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: ...

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 Shock metamorphism or impact metamorphism describes the effects of shock-wave related deformation and heating during impact events. The formation of similar features during explosive volcanism is generally discounted due to the lack of metamorp ...

, which can be determined from the size of a

shatter cone Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact craters or underground nuclear explosions. They are evidence that the rock has been subjected to a shock with pressures in the rang ...

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 nickel i ...

(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