Huntite

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Huntite is a carbonate mineral with the chemical formula Mg3Ca(CO3)4. It usually forms white, plate-like crystals or chalky masses in the trigonal crystal system. It’s a soft mineral (hardness 1–2) with an earthy luster and a white streak, and it often occurs together with other magnesium–calcium carbonates such as dolomite, magnesite, and hydromagnesite.

The mineral was identified in 1953 by George Faust from samples found in Currant Creek, Nevada. He named it huntite in honor of Walter Frederick Hunt, a professor of petrology. Analyses show that huntite has two endothermic steps when heated, corresponding to the breakdown of MgCO3 and CaCO3.

Today, huntite is mostly used in combination with hydromagnesite as a flame-retardant additive for polymers, offering an alternative to aluminum hydroxide. When exposed to fire, huntite releases carbon dioxide and absorbs heat, helping to slow the fire’s spread.

Large deposits are mined in Turkey and Greece for this purpose. Huntite has a wide range of natural occurrences, including carbonate sediments, salt lakes, playa lakes, and caves around the world. It has also been synthesized in laboratories since the 1960s, reflecting its close relationship to other carbonates like magnesite and dolomite. Historically, a mineral with the same composition was once referred to as conite, but that name is part of a more complex historical record and does not replace huntite’s current name.