Magnesite is a magnesium carbonate mineral calcined into the dense refractory magnesia used for refractory products in the cement, glass, and steel industries. This page covers that refractory role and what research shows about how natural magnesite compares to the alternative seawater-derived production route.
What is it?
Magnesite is a magnesium carbonate mineral, mined in the U.S. in Nevada. Per 2024 U.S. Geological Survey data, an estimated 22% of U.S. magnesium compound consumption went to refractory uses — dead-burned magnesia, fused magnesia, and olivine — with the remainder consumed as caustic-calcined magnesia and related compounds across environmental, chemical, agricultural, and deicing applications. Separately, per the USGS’s 2020 Minerals Yearbook, dead-burned and fused magnesias specifically (not olivine) were used for refractory products by the cement, glass, and steel industries.
Why should I use it?
- It’s calcined into dead-burned or fused magnesia with a documented refractory role in cement, glass, and steel production — see “What is it?” above.
- Research has directly studied how its crystal structure affects the calcination process needed to produce dense refractory magnesia — see Limitations.
How it’s used
In Glass and in Construction & Building Materials, magnesite is calcined into refractory magnesia used for refractory products in glass and cement manufacturing.
Limitations — when it isn’t the right choice
- How natural magnesite calcines into dense refractory magnesia depends on its crystal structure — a process tuned for one ore type won’t necessarily transfer to another. A 2020 peer-reviewed study compared macrocrystalline magnesite (from Liaoning) and cryptocrystalline magnesite (from Tibet) and found their endothermic decomposition peaks during calcination differ by 28°C (624°C for the cryptocrystalline sample versus 652°C for the macrocrystalline one). Older industry literature the study cites associates conventional natural-magnesite calcination with temperatures around 1900–2100°C to reach high-purity (>98% MgO), high-density refractory magnesia; the study’s own three-step process reached comparable density (3.47–3.48 g/cm³) at just 1670–1750°C, using magnesite feedstock already above 98% MgO purity. This was documented for two specific regional magnesite samples; it should not be assumed that every commercial magnesite deposit calcines identically, or that the same process temperature applies, without checking its own mineralogical data.
