Olivine facts for kids
Quick facts for kids Olivine |
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| General | |
| Category | Nesosilicate Olivine group Olivine series |
| Formula (repeating unit) |
(Mg, Fe)2SiO4 |
| Strunz classification | 9.AC.05 |
| Identification | |
| Color | Yellow to yellow-green |
| Crystal habit | Massive to granular |
| Crystal system | Orthorhombic |
| Cleavage | Poor |
| Fracture | Conchoidal – brittle |
| Mohs scale hardness | 6.5–7 |
| Luster | Vitreous |
| Streak | None |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.2–4.5 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.630–1.650 nβ = 1.650–1.670 nγ = 1.670–1.690 |
| Birefringence | δ = 0.040 |
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Olivine (or chrysolite) is a mineral made of magnesium iron silicate with the formula (Mg,Fe)2SiO4
It ranges in colour from chartreuse green to pale olive. In its gem form, it is called peridot.
Dunite is a rock of 90%+ olivine. Dunite and other peridotite rocks are major constituents of the Earth's mantle above a depth of about 400 kilometers. Dunite is rarely found on land, except where slabs of mantle rock from a subduction zone have been thrust onto continental crust. Olivine has also been found at several extraterrestrial locations, such as the moon and many passing space rocks - as well as the outer layers of dust orbiting young stars.
Uses
Olivine is used as a substitute for dolomite in steel works. Olivine is also used to tap blast furnaces in the steel industry, acting as a plug, removed in each steel run.
The aluminium foundry industry uses olivine sand to cast objects in aluminium. Olivine sand requires less water than silica sands while still holding the mold together during handling and pouring of the metal. Less water means less gas (steam) to vent from the mold as metal is poured into the mold.
In Finland, olivine is marketed as an ideal rock for sauna stoves because of its comparatively high density and resistance to weathering under repeated heating and cooling.
Images for kids
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Olivine in cross-polarized light
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Figure 1: The atomic scale structure of olivine looking along the a axis. Oxygen is shown in red, silicon in pink, and magnesium/iron in blue. A projection of the unit cell is shown by the black rectangle.
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Open-pit mining at Sunnylvsfjorden, Hurtigruten ship passing.
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Light green olivine crystals in peridotite xenoliths in basalt from Arizona
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Bright green olivine from Pakistan, showing chisel termination and silky luster
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Olivine in lava from the Azores
See also
In Spanish: Olivino para niños
