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4) are the two end-members of the olivine solid-solution series, varying in Mg 2+ and Fe 2+ in their chemical composition. So, the chemical formula of olivine can be better expressed as Mg (2−x) Fe x SiO 4 or Mg x Fe (2−x) SiO 4. As another example, the tectosilicate feldspar can be described as a solid solution of the endmembers K-feldspar ...
The mineral olivine (/ ˈ ɒ l. ɪ ˌ v iː n /) is a magnesium iron silicate with the chemical formula (Mg,Fe) 2 Si O 4.It is a type of nesosilicate or orthosilicate.The primary component of the Earth's upper mantle, [9] it is a common mineral in Earth's subsurface, but weathers quickly on the surface.
Fayalite (Fe 2 SiO 4, commonly abbreviated to Fa) is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system (space group Pbnm) with cell parameters a 4.82 Å, b 10.48 Å and c 6.09 Å.
Orange forsterite with a portion of tephroite. Pure forsterite is composed of magnesium, oxygen and silicon. The chemical formula is Mg 2 SiO 4.Forsterite, fayalite (Fe 2 SiO 4) and tephroite (Mn 2 SiO 4) are the end-members of the olivine solid solution series; other elements such as Ni and Ca substitute for Fe and Mg in olivine, but only in minor proportions in natural occurrences.
Monticellite and kirschsteinite (commonly also spelled kirschteinite [3]) are gray silicate minerals of the olivine group with compositions Ca Mg Si O 4 and CaFeSiO 4, respectively.. Most monticellites have the pure magnesium end-member composition but rare ferroan monticellites and magnesio-kirschsteinite are found with between 30 and 75 mol.% of the iron end memb
Because minerals are natural materials they are prone to large variations in composition. In many cases specimens are members for a solid solution family and geologists find it more helpful to discuss the composition of the family than an individual specimen. Olivine is described by the formula (Mg, Fe) 2 SiO 4, which is equivalent to (Mg 1−x ...
On the other hand, some substances that have a continuous series of compositions, may be arbitrarily split into several minerals. The typical example is the olivine group (Mg, Fe) 2 SiO 4, whose magnesium-rich and iron-rich end-members are considered separate minerals (forsterite and fayalite). The details of these rules are somewhat ...
The serpentinization reaction involving the transformation of fayalite (Fe-end member of olivine) by water into magnetite and quartz also produces molecular hydrogen H 2 according to the following reaction: + + +