Olivine Definition
The Olivine is a mineral that is basically iron silicon blended with magnesium. The olivine chemical formula is (Mg2+Fe2+)2SiO4. It is considered to be a type of orthosilicate and nesosilicate. The main element of the upper mantle of Earth, it is a standard mineral in the subsurface of Earth; however, it weathers rapidly on the Earth’s surface. Because of this reason, it is considered to be the best element for accelerated weathering to CO2 (sequester) from the oceans or atmosphere of Earth. With the current situation of climatic changes, it is considered to be the best element.
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What is the Ratio of Elements included in Olivine?
Olivine primarily has two elements: iron and magnesium. The ratio between these two elements varies when the two endmembers of a solution are formed. This solution includes forsterite and fayalite. These compositions are usually expressed in the form of molar percentages. The melting temperature of forsterite is quite high under atmospheric pressure. It has a temperature of more than 1,900 degrees centigrade. However, when it comes to fayalite, the temperature is often recorded to stand at 1,200 degrees centigrade. The melting temperature often varies when it comes to both of these endmembers and the other properties.
Olivine has minor elements that include oxygen, silicon, magnesium, and iron. Besides this, Manganese and Nickel are some other elements that are present in Olivine in huge concentrations. The crystal structure of Olivine also has aspects that include orthorhombic P Bravais lattice. This arises from the SiO4 (Silica) units joined by many divalent cations of metals with oxygen in the silica that is again bound to just three ions of metals. It also has spinel-like elements that are equivalent to magnetite; however, it just uses a single quadrivalent and a couple of divalent cations.
What is the Identification of Olivine?
The name Olivine is introduced because of its usual olive-green color element. However, it can also alter its color to red if the iron oxide is formed from the equation.
The translucent iron is mostly used in the form of gemstone that is called peridot. Also, many people call it chrysolite, which means gold and stone in Greek. However, both of these names are not much use when it comes to the English language. Many finest Olivine is obtained from mantle rocks that are present in the Red Sea.
Where does Olivine Occur?
Olivine mineral occurs in both the magic as well as ultramafic igneous olivine rock. It also occurs in many other metamorphic rocks. Mg-rich crystallizes Olivine from magma has low concentrations of silica and more concentrations in magnesium. This magma then crystallizes to those mafic rocks that include gabbro, basalt, and others. The ultramafic rocks also have substantial Olivine.
Many elements having more than 40 percent of Olivine is known as peridotites. If you are looking for olivine meaning, then it is a complex silicate that includes magnesium as well as iron that is used in refractories.
Any element that has more than 90 percent of olivine content they are called Dunite. It accumulates to form crystallization and settle out of magma. Olivine and other materials constitute over about 50 percent of the upper mantle of the Earth. It is of the common minerals that are available in most common across all the world. The metamorphism or any other sedimentary rocks that have high magnesium or low silicon content also produces Olivine in huge quantities.
Fe-rich fayalite is not available in common and occurs only on igneous rocks in minimal amounts. It is available in rare places that have granites or rhyolites. Fe-rich olivine content can only be present if there are stable quantities of quartz or tridymite available. On the other hand, Mg-rich olivine is not available where silica minerals are available. It would react and form an orthopyroxene compound.
Where does Olivine Do in Extra-Terrestrial Regions?
It is discovered that Olivine is also available in meteorites on the Mars Planet or Moon. It falls into the infant stars and on asteroid 25143 Itokawa. There are many meteorites that are available, which includes chondrites and other debris collections from pallasites, iron-nickel regions, and Olivine.
FAQs on Olivine
1. What is Olivine and where is it primarily found within the Earth's structure?
Olivine is a group of rock-forming nesosilicate minerals with the chemical formula (Mg, Fe)₂SiO₄. It is a major component of the Earth's upper mantle. While abundant in the subsurface, it weathers quickly on the surface. Olivine is primarily a blend of two endmembers: Forsterite (magnesium-rich) and Fayalite (iron-rich).
2. How is Olivine identified based on its physical properties?
Olivine is typically identified by its characteristic olive-green colour, which gives the mineral its name. It has a glassy lustre, a conchoidal fracture, and a hardness ranging from 6.5 to 7 on the Mohs scale. Its colour can sometimes alter to a reddish hue due to the oxidation of iron within its structure.
3. What are the main applications of Olivine in industry and environmental science?
Olivine has several important applications, including:
- Steel Production: It is used as a slag conditioner and an alternative to dolomite in steelworks.
- Foundry Sand: In the aluminium foundry industry, it is used as a moulding sand.
- Carbon Sequestration: Olivine is studied for its potential in enhanced weathering. When crushed, it reacts with atmospheric carbon dioxide (CO₂), effectively sequestering it as stable magnesium carbonate. This makes it a promising tool for mitigating climate change.
4. What is the relationship between Olivine and the gemstone Peridot?
Peridot is the gem-quality variety of Olivine. While Olivine is a common mineral, only a small fraction of it possesses the transparency, colour, and clarity required to be considered a gemstone. Therefore, all Peridot is Olivine, but not all Olivine is Peridot. The name 'chrysolite' has also been used historically for this gemstone.
5. Why is Mg-rich Olivine common in mafic and ultramafic rocks but not found alongside silica minerals like quartz?
This is due to chemical stability. Mg-rich Olivine (Forsterite) crystallises from magmas that are high in magnesium and iron but low in silica. If free silica, such as quartz, were present in such a magma, it would react with the Olivine to form a different mineral, orthopyroxene ( (Mg,Fe)₂Si₂O₆ ). This reaction prevents Olivine and quartz from coexisting in equilibrium in most igneous rocks.
6. What does the crystal structure of Olivine tell us about its classification as a nesosilicate?
Olivine's crystal structure consists of isolated silica tetrahedra (SiO₄) that are not linked to each other. Instead, these tetrahedra are bonded together by magnesium (Mg²⁺) and iron (Fe²⁺) ions. Because the silica tetrahedra are independent, Olivine is classified as a nesosilicate, or orthosilicate, which is the simplest type of silicate structure.
7. What is the significance of finding Olivine on other celestial bodies like Mars and asteroids?
The discovery of Olivine on Mars, the Moon, and asteroids like 25143 Itokawa provides crucial insights into their geological history. Since Olivine weathers quickly in the presence of water, its existence on the Martian surface suggests that some regions have been very dry for long periods. Its presence in meteorites also helps scientists understand the composition and formation of the early solar system and the interiors of other planetary bodies.
