Alunite: The Volcanic Mineral Once Chased as a Key to Eternal Life

Nature · Published 3 October 2026 Swipe more like this →

In short: Beyond its industrial history as a source of potash and alumina, this widespread sulfate mineral has a strange, mystical past. Thousands of years ago, Chinese alchemists combined alunite with potassium nitrate in a failed attempt to concoct a legendary elixir of immortality, leaving behind a curious archaeological footprint.

Alunite is a hydroxylated aluminium potassium sulfate mineral, chemically defined as KAl3(SO4)2(OH)6. It typically forms in volcanic environments, appearing as veins or replacement masses within potassium-rich rocks like rhyolite, trachyte, and andesite. Its creation is often linked to the chemical reaction between these volcanic rocks and sulfurous vapors or sulfuric acid-bearing solutions, frequently occurring near fumaroles or during the oxidation of metal sulfide deposits.

The mineral’s history is deeply intertwined with human industry. Since the 15th century, it has been mined for the production of alum. Its utility expanded during the 20th century, serving as a vital source of potash during World War I and alumina during World War II. Its physical characteristics—a Mohs hardness of 4 and a trigonal crystal structure—have even made it useful for practical applications like millstones, particularly the compact varieties found in Hungary.

Beyond Earth, alunite has become a subject of intense scientific interest for its presence on Mars. Researchers have identified the mineral in locations like Cross crater, using it as evidence of past acidic, sulfurous water activity on the Martian surface. By studying terrestrial analogs in places like the Basque Lakes in British Columbia or Goldfield, Nevada, scientists are better able to interpret the geological history of the Red Planet.

While its modern value lies in geology and planetary science, its historical reputation was far more esoteric. In 2019, archaeologists in Henan province, China, discovered 2,000-year-old ceramic jars containing a mixture of alunite and potassium nitrate. This discovery aligned with ancient texts describing a 'mixture of immortality,' a testament to the mineral's long-standing, if ultimately unsuccessful, role in the human pursuit of eternal life.

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