OlivineEdit

Olivine is a mineral group that represents the solid solution between the two endmembers forsterite (Mg2SiO4) and fayalite (Fe2SiO4). As a member of the silicate family, olivine is an iron- and magnesium-rich mineral with a characteristic olive-green to yellow-green color in many samples. It crystallizes in the orthorhombic system and forms under high-temperature conditions, making it a dominant constituent of ultramafic rocks and the Earth's upper mantle. In the laboratory and in the field, olivine is a fundamental clue to understanding magmatic differentiation, mantle composition, and planetary geology. Gem-quality olivine is widely known as peridot, the gem variety that captivates collectors and jewelers with its bright, lime-green hues. silicate Forsterite Fayalite peridot

Olivine’s importance in geology stems from its prevalence in mantle-derived rocks such as peridotite and dunite, as well as its common occurrence in basaltic lavas and related magmas. It forms early during the cooling of mafic and ultramafic magmas and tends to crystallize before many other minerals in these systems, helping to shape the suite of minerals that record the history of magmatic differentiation. In addition to crustal rocks, olivine appears in various meteorites, including pallasites, where it coexists with other minerals in a way that informs us about early solar-system processes. The polymorphous nature of olivine—its substitution of magnesium and iron across a continuous solid solution—reflects the variable conditions under which rocks form and evolve. basalt mantle peridotite pallasite

Structure and composition

Endmembers: forsterite (Mg2SiO4) and fayalite (Fe2SiO4). The mineral commonly exists as a solid solution between these two endmembers, producing a range of Mg-Fe compositions. The chemical formula can be written as (Mg,Fe)2SiO4. Forsterite Fayalite
Crystal system and properties: olivine is orthorhombic, typically forms granular to equant crystals, and shows a relatively high melting point. Its hardness on the Mohs scale is around 6.5–7, and its specific gravity is approximately 3.2–3.4. The color ranges from green to yellow-green in many specimens, with deeper greens in iron-poor varieties. These properties contribute to olivine’s role in high-temperature rocks and in refractory materials. crystal system Mohs scale
Gem and industrial forms: gem-quality olivine occurs as the mineral variety known as peridot, prized for its vivid green color. In industrial contexts, olivine minerals—particularly magnesium-rich forsterite—are used in refractories and as a source of magnesium for various industrial applications. peridot refractory material

Geology and occurrence

Olivine is a hallmark mineral of the Earth’s mantle and ultramafic crust. In the mantle, olivine remains stable at a wide range of depths and temperatures, making it a major constituent of rocks such as peridotite and harzburgite. Its presence tracks the differentiation and melting histories of mantle rocks, and it helps constrain models of mantle convection and tectonic behavior. In the crust, olivine crystallizes from basaltic magmas and appears as phenocrysts or groundmass grains, contributing to the texture and evolution of basaltic rocks. Olivine is also found in meteorites, where it records the mineralogy of early solar-system bodies and the processes that formed planetary materials. mantle ultramafic basalt meteorite pallasite

Formation, alteration, and behavior

Formation: olivine crystallizes from silica-poor, magnesium- and iron-rich magmas and can crystallize early as the melt cools. Its stability and composition reflect the balance of Mg and Fe in the melt and surrounding rocks. This makes olivine a useful mineral for interpreting magmatic differentiation paths. magma
Alteration: under surface conditions, olivine can alter to secondary minerals such as serpentine and various clays, depending on fluid interactions. The alteration products and textures provide information about post-emplacement histories of rocks. alteration
Significance in planetary science: olivine-rich rocks have been identified in Martian meteorites and on planetary bodies, contributing to our understanding of their geological histories. The study of olivine in extraterrestrial samples helps researchers compare Earth’s interior processes with those on other worlds. Mars planetary geology

Economic and practical aspects

Olivine-bearing rocks contribute to economic geology through their role in mining and industrial applications. Magnesium-rich olivine (forsterite) is used in refractories due to its high melting point and stability at high temperatures, which is important for metallurgical processes and high-temperature industrial equipment. The gem-quality form, known as peridot, is mined for jewelry and decorative use. The distribution of olivine in the crust and mantle also informs policies around mineral rights, exploration incentives, and regulatory frameworks in resource-rich regions. As with many natural resources, economic value depends on market demand, extraction costs, and environmental considerations tied to mining and processing. refractory material mineral rights

Controversies and debates (in context)

In the broader conversations about geology and resource policy, debates tend to center on how best to balance exploration with environmental stewardship, and how to fund basic research that translates into practical technology. While olivine itself is a well-established mineral with clear geological significance, discussions about mining regulation, land use, and public-private partnerships reflect ongoing policy debates in many jurisdictions. From a scientific perspective, the interpretation of mantle processes, partial melting, and mantle-crust interaction continues to evolve with new data from seismic studies, high-pressure experiments, and planetary samples. The underlying science remains robust, and the practical implications—such as the use of olivine-rich materials in refractories—are generally driven by market forces and engineering needs. seismic studies high-pressure experiments planetary samples