olivine


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olivine

(ŏlĭv`ēn), an iron-magnesium silicate mineral, (Mg,Fe)2SiO4, crystallizing in the orthorhombic system. It is a common constituent of magnesium-rich, silica-poor igneous rocks; metamorphism of some high magnesium sediments also can form olivine. Dunite consists almost entirely of olivine. It also occurs in lunar rocks and meteorites. Olivine has a characteristic yellow-green to olive-green color, hence the name. Transparent olivine of good color can be cut into gemstones; the gem form is known as peridot. Sources of gem-quality olivine are St. John's Island in the Red Sea, Myanmar, and Arizona. Magnesium-rich olivine has a high melting point and is used in the manufacture of refractories. It was formerly called chrysolite.

Olivine

 

(also peridot or chrysolite), a mineral of the neso-silicate class; the main representative of the olivine group. The olivine group includes forsterite, Mg2[SiO4]; olivine, (Mg,Fe)2[SiO4]; fayalite, Fe2[SiO4]; tephroite, Mn2[SiO4]; knebelite, (Fe,Mn)2[SiO4]; and monticellite, CaMg[SiO4].

The minerals of the olivine group differ from one another in both properties and composition. They crystallize in the ortho-rhombic system to form tabular or prismatic crystals. The olivine structure is composed of isolated tetrahedral SiO44- groups and of Mg2+ and Fe2+ cations surrounded by six oxygen ions. The structural distribution of magnesium and iron, as determined by Mössbauer spectra, serves as a geothermometer. Olivine has imperfect cleavage; its hardness on Mohs’ scale is 6.5–7.0, and its density is 3,200–4,400 kg/m3, depending on the number of heavy iron and manganese atoms per molecule. Its color varies from yellowish green to olive green; sometimes the mineral is colorless.

Olivine is widespread in nature as a rock-forming mineral in ultrabasic and basic rocks, such as dunites, peridotites, olivine gabbros, diabases, and basalts, including lunar basalt. The olivine structure rearranges to form a spinel-type lattice under high pressure (130–160 kilobars). The effect of hydrothermal solutions readily alters olivine into serpentine and sometimes also to talc. On the earth’s surface, olivine decomposes to yield magne-site, hydrous iron oxides, and opal. Transparent olivine crystals, or chrysolites, are precious stones.

REFERENCE

Mineraly: Spravochnik, vol. 3, fasc. 1. Moscow, 1972.

olivine

[′äl·ə‚vēn]
(mineralogy)
(Mg,Fe2)SiO4 A neosilicate group of olive-green magnesium-iron silicate minerals crystallizing in the orthorhombic system and having a vitreous luster; hardness is 6½-7 on Mohs scale; specific gravity is 3.27-3.37.
References in periodicals archive ?
Kremer and his colleagues are hoping that the lander will study the olivine mineral and obtain more data that could help either prove or disprove their explosive eruption suggestion.
At 700[degrees]C, the cobalt ferrite formation is more thermodynamically favored than the formation of olivine. The FT-IR spectra (Figure 3(b)) show characteristic bands for Co[Fe.sub.2][O.sub.4] (466 and 594 [cm.sup.-1]) and silica matrix (480, 798, 1080, 1650, and 3400-3500 [cm.sup.-1]) [25, 26, 31, 32].
Olivine occurs as corroded, anhedral, individual or clusters of cumulus grains, poikilitically included in intercumulus augite (Fig.
It is made up mostly of silicate minerals olivine and pyroxene which reacts with carbon dioxide, it converts the gas into calcite, a solid mineral, said an expert.
The remote sensing data for Chang'e-3's landing site showed that it was rich in olivine as well as titanium.
The meteorites originating from Vesta and found on Earth confirm this since they generally lack Olivine, or contain only minute amounts compared to the amount observed in planetary mantles.
In the process, olivine turns into the mineral serpentine and water splits into its components, hydrogen and oxygen.
The Dempson BAG[R] has a unique 'wide bottom' which the Olivine container sits neatly in, making transport from the point of purchase to the point of consumption easy and hassle free.
When scientists Philipp Ruprecht and Terry Plank of Columbia University's Lamont-Doherty Earth Observatory examined tiny crystals of the mineral olivine, they saw much more nickel than expected.
Unusual minerals like spinel and olivine found in many lunar craters, but rarely on the Moon's surface, were therefore attributed to the excavation of sub-surface lunar layers by asteroid hits.
Raymond was born October 16, 1918 in Worcester, son of the late Olivine (Deloge) and John Fontaine.