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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.
Kimberlite: formed in volcanic pipes and at least 35% olivine [9] Kimberlite is a highly brecciated variant of peridotite formed in volcanic pipes and is known for being the host rock to diamonds. Unlike other forms of peridotite, kimberlite is quite rare. [10] Pyroxene peridotite: From 40% to 90% olivine and less than 5% hornblende
Peridot olivine is the birthstone for the month of August. [17] Peridot has often been mistaken for emerald beryl and other green gems. [18] Noted gemologist G.F. Kunz discussed the confusion between beryl and peridot in many church treasures, most notably the "Three Magi treasure" in the Dom of Cologne, Germany. [19] [1]
Observations of rocks exposed on the surface and other evidence reveal that the upper mantle is mafic minerals olivine and pyroxene, and it has a density of about 3.33 g/cm 3 (0.120 lb/cu in) [1] Upper mantle material that has come up onto the surface comprises about 55% olivine and 35% pyroxene, and 5 to 10% of calcium oxide and aluminum oxide ...
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.
The mafic rocks also typically have a higher density than felsic rocks. The term roughly corresponds to the older basic rock class. [9] Mafic lava, before cooling, has a low viscosity, in comparison with felsic lava, due to the lower silica content in mafic magma. Water and other volatiles can more easily and gradually escape from mafic lava.
Mineralogically, labradorite is a compositional term for any calcium-rich plagioclase feldspar containing 50–70 molecular percent anorthite (An 50–70), regardless of whether it shows labradorescence. The mafic mineral in Proterozoic anorthosite may be clinopyroxene, orthopyroxene, olivine, or, more rarely, amphibole.
The distinctive characteristic of olivine lamproites is phlogopite macrocrysts and microphenocrysts, together with groundmass micas that vary in composition from phlogopite to "tetraferriphlogopite" (anomalously Al-poor phlogopite requiring Fe to enter the tetrahedral site). Resorbed olivine macrocrysts and euhedral primary crystals of ...