right|thumb|Leonardite, naturally Redox|oxidized [[lignite, rich in humic acid]]
right|thumb|Leonardite, naturally Redox|oxidized [[lignite, rich in humic acid]]
Leonardite is a soft waxy, black or brown, shiny, vitreous mineraloid that is easily soluble in alkaline solutions. It is an oxidation product of lignite, associated with near-surface mining. It is a rich source of humic acid (up to 90%) and is used as a soil conditioner, as a stabilizer for ion-exchange resins in water treatment, in the remediation of polluted environments and as a drilling additive. It was named after A. G. Leonard, first director of the North Dakota Geological Survey, in recognition of his work on these deposits.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).