Deep-sea mineral samples spontaneously combust in laboratory tests

Researchers from the U.S. Geological Survey (USGS) have discovered that certain mineral-rich rocks collected from the ocean floor can spontaneously ignite when exposed to air. During laboratory testing of samples retrieved from the Escanaba Trough in the northeast Pacific Ocean, two of the 57 samples reached temperatures exceeding 100°C and began emitting smoke.

The study, published in Scientific Reports, identified nanocrystalline marcasite—an iron sulfide mineral—as the cause. When exposed to oxygen, the mineral reacts and releases heat. The process can be triggered by physical stressors such as crushing, fracturing, or grinding the rocks, which provides enough energy to initiate oxidation and subsequent self-heating.

These findings serve as a warning for the emerging deep-sea mining industry. While large-scale commercial operations have not yet begun, companies are currently conducting technological trials. The Escanaba Trough, located along the Gorda Ridge off the coast of the United States, contains significant deposits of metals including zinc, copper, and iron, making it a primary area of interest for mineral extraction.