Olivine is a common mineral, a magnesium iron silicate that forms in high-temperature environments deep within the Earth’s mantle and crust. It receives its name from its characteristic yellowish-green color, similar to a ripe olive. Although it is a significant component of many volcanic rocks, its unique physical and chemical properties allow it to be used in a surprising number of consumer and industrial applications.
Olivine as a Gemstone
Many people encounter olivine in its transparent, gem-quality form, known commercially as peridot. This gemstone occurs only in shades of green, ranging from pale yellow-green to an intense, deep olive hue. Peridot’s distinct color comes from the presence of iron within the mineral’s structure. Historically, it has been a popular choice for jewelry, including rings, necklaces, and pendants, and is the birthstone for August.
Peridot’s appeal lies in its vibrant color and hardness (6.5 to 7 on the Mohs scale), making it suitable for daily wear when properly cut. While olivine is geologically abundant, large, flawless peridot crystals are less common, contributing to its value. Ancient sources of the gem, such as those on an island in the Red Sea, supplied many of the magnificent stones found in historical European collections.
High-Temperature Manufacturing Applications
Olivine is highly valued in heavy industry for its ability to withstand extremely high temperatures. This property makes it a preferred material in the metalworking industry, where it is used in specialized foundry processes. Olivine sand serves as a mold and core material for casting metals, particularly manganese steel and non-ferrous alloys. It ensures the final cast product has a smooth surface finish and dimensional stability.
Furthermore, olivine is incorporated into refractory materials, which are used to line furnaces and kilns in steel and glass production. These refractory products, like bonded forsterite bricks, are engineered to resist the intense heat and chemical reactions occurring inside industrial vessels. Its chemical stability and high magnesium content also allow it to be used as a fluxing agent in blast furnaces, where it helps remove impurities from molten iron during steel production.
Role in Enhanced Weathering and Carbon Capture
A different application for olivine is in climate change mitigation, specifically through enhanced weathering. This technique artificially accelerates the natural geological process by which silicate rocks remove carbon dioxide (CO₂) from the atmosphere. Olivine is a prime candidate for this application because it weathers faster than many other silicate minerals. The process involves mining the rock, crushing it into a fine powder to maximize surface area, and dispersing it across land or ocean environments.
When the pulverized olivine reacts with water and atmospheric CO₂, a chemical transformation occurs where the carbon is captured. The carbon dioxide is permanently converted into stable, solid compounds, such as magnesium bicarbonate, which remains sequestered from the atmosphere. This method is being explored as a large-scale strategy, with proposals to spread the material on agricultural fields or coastal beaches to accelerate the carbon removal cycle. Early studies suggest that this application could also help counteract ocean acidification by increasing the alkalinity of seawater.
Specialized Thermal Storage Uses
Olivine’s heat-resistant properties are also harnessed to store and radiate thermal energy in consumer appliances. Unlike its use in manufacturing, this application leverages the mineral’s high density to absorb heat efficiently. This makes it a preferred material for the heat storage cores in modern night storage heaters.
In these residential heating systems, embedded electrical elements heat the olivine bricks to high temperatures during off-peak hours when electricity rates are lower. The dense mineral core then slowly releases the stored thermal energy over the course of the day. Similarly, olivine stones are used in sauna stoves, where they are heated and then radiate a gentle, consistent warmth for an extended period.