Leonardite is a soft waxy, black or brown, shiny, vitreous

mineraloid A mineraloid is a naturally occurring mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an a ...

that is easily soluble in alkaline solutions. It is an

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

product of

lignite Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...

, associated with near-surface

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the econom ...

. It is a rich source of

humic acid Humic substances (HS) are organic compounds that are important components of humus, the major organic fraction of soil, peat, and coal (and also a constituent of many upland streams, dystrophic lakes, and ocean water). For a long era in the 19th an ...

(up to 90%) and is used as a

soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...

, as a stabilizer for ion-exchange resins in water treatment, in the remediation of polluted environments and as a

drilling Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at ...

additive.Hoffman, G.L., Nikols, D.J., Stuhec, S., Wilson, R.A. Evaluation of Leonardite (Humalite) Open File Report 1993-18, Resources of Alberta, Alberta Geological Survey
It was named after A. G. Leonard, first director of the North Dakota Geological Survey, in recognition of his work on these deposits.Odzoba, D.M., Blyth, J.C., Engler, R.F., Dinel, H. & Schnitzer, M. 2001. Leonardite and humified organic matter. In Ghabbour, E.A. & Davies, G. (eds.) Humic Substances: Structures, Models and Functions (Special Publication), Royal Society of Chemistry 388pp.

Formation

Leonardite is found associated with near surface lignite deposits. They are thought to have been formed by the oxidation of the lignite, an interpretation supported by chemical analysis of leonardite compared to lignite.Youngs, R.W. & Frost, C.M. 1963. Humic acids from leonardite – a soil conditioner and organic fertilizer. Ind. Eng. Chem., 55, 95–99
/ref>

Occurrence

Leonardite was first described from North Dakota and is found associated with virtually all the lignite deposits in the state. Leonardite has also been described worldwide from deposits of lignite or sub-bituminous coals e.g. in

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest T ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...

, in

Achlada Achlada ( el, Αχλάδα, before 1926: Κρουσοράτη - ''Krousorati''; bg, Крушоради, ''Krushoradi'', Macedonian: , ''Krušoradi'') is a village in the Florina regional unit, Western Macedonia, Greece. History The settlement ...

and Zeli,

Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders wi ...

, in

Turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula ...

and in

Bacchus Marsh Bacchus Marsh ( Wathawurrung: ''Pullerbopulloke'') is an urban centre and suburban locality in Victoria, Australia located approximately north west of the state capital Melbourne and west of Melton at a near equidistance to the major cities ...

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

Uses

Soil conditioner

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 Potassium humate is the potassium salt of humic acid. It is manufactured commercially by alkaline extraction of brown coal (lignite) leonardite and is used mainly as a soil conditioner. Extraction The extraction is performed in water with the ad ...

for application. The carbon geosequestration potential of Leonardite, particularly to rapidly accelerate microbial action to lock up and retain carbon in soils, provides the basis for extensive research in

Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...

on the organic fertilising aspect of brown coal.

Remediation of polluted soils

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

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...

Drilling additive

Leonardite is used to stabilise and thin fluids used in the drilling of wells for hydrocarbon exploration/extraction and geothermal drilling. It was first employed extensively during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

when quebracho became difficult to obtain.Darley, H.C.H. & Gray, D.R. 1988. Composition and properties of drilling and completion fluids, Gulf Professional Publishing, 644pp.
/ref> It has very good temperature stability and prevents solidification of lime muds near 150 °C.

References

External links

{{Commons category
Victoria Australia Brown Coal Factsheet
Coal Organic minerals Soil improvers