Leonardite

Leonardite is a soft waxy, black or brown, shiny, vitreous mineraloid that is easily soluble in alkaline solutions.

[1] It is a rich source of humic acid (up to 90%)[2] and is used as a soil conditioner, as a stabilizer for ion-exchange resins in water treatment,[3] in the remediation of polluted environments and as a drilling additive.

[6] Leonardite has also been described worldwide from deposits of lignite or sub-bituminous coals e.g. in Alberta, Canada,[4] in Achlada and Zeli, Greece,[7] in Turkey and in Bacchus Marsh, Australia.

[8] It is used to condition soils either by applying it directly to the land, or by providing a source of humic acid or potassium humate for application.

[9] Leonardite can be added directly to soils to reduce the uptake of metals by plants in contaminated ground, particularly when combined with compost.