Product Code Database
Rock flour, or glacial flour, consists of fine-grained, silt-sized particles of rock, generated by mechanical grinding of bedrock by glacial erosion or by artificial grinding to a similar size. Because the material is very small, it becomes suspended in meltwater making the water appear cloudy, which is sometimes known as glacial milk. "Glossary of Terms: G: Glacial Milk" PhysicalGeography.netGornitz, Vivien (editor) (2007) "Glacial Geomorphology" pp. 361–374 Encyclopedia of paleoclimatology and ancient environments Springer Netherland, Berlin, page 365,
When the sediments enter a river, they turn it grey, light brown, iridescent blue-green, or milky white. If the river flows into a glacial lake, the lake may appear turquoise in colour as a result. When flows of the flour are extensive, a distinct layer of a different colour flows into the lake and begins to dissipate and settle as the flow extends from the increase in water flow from the glacier during snow melts and heavy rain periods. Examples of this phenomenon may be seen at Lake Pukaki and Lake Tekapo in New Zealand, Lake Louise, Moraine Lake, Emerald Lake, and Peyto Lake in Canada, Gjende lake in Norway, and several lakes (among others, Nordenskjöld and Pehoé) in Chile's Torres del Paine National Park, and many lakes in the Cascade Range of Washington State (including Diablo Lake, Gorge Dam, and Blanca Lake).
Although clay-sized, the flour particles are not clay minerals but typically ground up quartz and feldspar. Rock flour is carried out from the system via meltwater streams, where the particles travel in suspension. Rock flour particles may travel great distances either suspended in water or carried by the wind, in the latter case forming deposits called loess.
The basalt and granite often contain the highest mineral content, whereas limestone, considered inferior in this consideration, is often deficient in the majority of essential macro-compounds, trace elements, and .
Rock dust is added to soil to improve fertility and has been tested since 1993 at the Sustainable Ecological Earth Regeneration Centre (SEER Centre) in Straloch, near Pitlochry, in Perth and Kinross, Scotland.Remineralization Might Save Us From Global Warming, The Independent, Paul Kelbie, 21 March 2005 Further testing has been undertaken by James Cook University, Townsville, Far North Queensland.
John D. Hamaker argued that widespread remineralization of soils with rock dust would be necessary to reverse soil depletion by current agriculture and forestry practice.
While this originally was an alternative concept, increasing mainstream research has been devoted to soil amendment and other benefits of rock flour application: for instance, a pilot project on the use of glacial rock, granite and fines by the U.S. Department of Agriculture exists at the Henry A. Wallace Beltsville Agricultural Research Center. The SEER Centre in Scotland is a leading source of information on the use of rock dusts and mineral fines. The Soil Remineralization Forum was established with sponsorship from the Scottish Environment Protection Agency and has commissioned a portfolio of research into the benefits of using mineral fines. The Forum provides an interface among research, , and industry.
A 2022 study found that basalt dust improved soil fertility and increased available phosphorus, potassium, calcium and magnesium levels compared to soil without the basalt dust in a period of several months.
Greenland rock flour increased yields from corn fields in Ghana and barley fields by 30-50%. Melting ice is depositing one billion tons of rock flour annually; one ton can direct air capture of carbon.
In forestry, rock flour can gradually increase the pH and buffering status of soils via its slow-release liming properties and increase tree radial growth if nitrogen is not deficient, even up to 34 years after the application. Furthermore, rock flour amended in the planting pits of tree saplings can increase sapling survival and growth when reforesting acidified forest soils.
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| calcium | %w/w | 6.44 |
| iron | %w/w | 10.5 |
| magnesium | %w/w | 6.54 |
| sulfur | %w/w | 0.21 |
| potassium | %w/w | 1.25 |
| phosphorus | mg/kg | 3030 |
| cobalt | mg/kg | 35 |
| copper | mg/kg | 43 |
| manganese | mg/kg | 790 |
| molybdenum | mg/kg | <5 |
| zinc | mg/kg | 92 |
| silicon | %w/w | 21.6 |
Often phosphorus is locked in soils due to many years of application of traditional . The use of micronutrient-rich fertiliser enables plants to access locked phosphorus.
The Chemical element high in available 2+ valence electrons, calcium, iron and magnesium in particular contribute to paramagnetism in soil which aid in cation exchange capacity.
The calcium and magnesium in high quality have the ability to neutralise pH in soils, in effect acting as a liming agent.
In some soils which display poor levels of nutrients, application rates of 10 up to 50 tonnes per hectare are required. In Australia, namely the Riverland, Riverina, Langhorne Creek, Barossa Valley and McLaren Vale regions, rates are 3–5 tonnes per hectare. In a garden application, this might equate to 400 grams per square metre.
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