# Hydromagnesite

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Hydromagnesite
> Markdown URL: https://mediated.wiki/source/Hydromagnesite.md
> Source: https://en.wikipedia.org/wiki/Hydromagnesite
> Source revision: 1288290090
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Hydrated hydroxy-carbonate mineral of magnesium

Hydromagnesite Hydromagnesite balloon in Jewel Cave General Category Carbonate mineral Formula Mg5(CO3)4(OH)2·4H2O IMA symbol Hmgs[1] Strunz classification 5.DA.05 Dana classification 16b.07.01.01 Crystal system Monoclinic Crystal class Prismatic (2/m) (same H-M symbol) Space group P21/c Identification Formula mass 467.64 g/mol Color Colorless, white Crystal habit Acicular and as encrustations; pseudo-orthorhombic Twinning Polysynthetic lamellar on {100} Cleavage {010} Perfect, {100} Distinct Fracture Uneven Tenacity Brittle Mohs scale hardness 3.5 Luster Vitreous, silky, pearly, earthy Streak White Diaphaneity Transparent to translucent Specific gravity 2.16–2.2 Optical properties Biaxial (+) Refractive index nα = 1.523 nβ = 1.527 nγ = 1.545 Birefringence δ = 0.022 Ultraviolet fluorescence Fluorescent, short UV=green, long UV=bluish white. References [2][3][4]

**Hydromagnesite** is a hydrated [magnesium](/source/Magnesium) [carbonate mineral](/source/Carbonate_mineral) with the formula Mg5(CO3)4(OH)2·4H2O.

It generally occurs associated with the weathering products of magnesium containing minerals such as [serpentine](/source/Serpentine_group) or [brucite](/source/Brucite). It occurs as incrustations and vein or fracture fillings in [ultramafic rocks](/source/Ultramafic_rock) and [serpentinites](/source/Serpentinite), and occurs in [hydrothermally](/source/Hydrothermal) altered [dolomite](/source/Dolomite_(rock)) and [marble](/source/Marble). Hydromagnesite commonly appears in [caves](/source/Cave) as [speleothems](/source/Speleothem) and "[moonmilk](/source/Moonmilk)", deposited from water that has seeped through magnesium rich rocks. It is the most common cave carbonate after [calcite](/source/Calcite) and [aragonite](/source/Aragonite).[2] The mineral thermally decomposes,[5][6] over a temperature range of approximately 220 °C to 550 °C, releasing water and carbon dioxide leaving a magnesium oxide residue.

Hydromagnesite was first described in 1836 for an occurrence in [Hoboken, New Jersey](/source/Hoboken%2C_New_Jersey).[3]

[Stromatolites](/source/Stromatolite) in an [alkaline](/source/Alkaline) ([pH](/source/PH) greater than 9) freshwater lake ([Salda Gölü](/source/Lake_Salda)) in southern [Turkey](/source/Turkey) are made of hydromagnesite precipitated by [diatoms](/source/Diatom) and [cyanobacteria](/source/Cyanobacteria).[7]

SEM micrograph of hydromagnesite showing platy crystal morphology.  Sample was collected from the hydromagnesite-magnesite playas near Atlin, British Columbia, Canada.[8]

Microbial deposition of hydromagnesite is also reported from [playas](/source/Dry_lake) in [British Columbia](/source/British_Columbia).[9] The hydromagnesite-magnesite playas near Atlin, British Columbia are some of the most studied deposits of hydromagnesite. These deposits have been characterized in the context of a biogeochemical model for [CO2 sequestration](/source/CO2_sequestration).[8]

One of the largest deposits of hydromagnesite exists in Greece.[10] It consists of a natural mixture with [huntite](/source/Huntite). Local people have used the white mineral as a source of material for whitewashing buildings for centuries. In the mid 20th century the minerals, ground to a fine powder, found use as a filler for rubber shoe soles. The locals used the granite mills designed for grinding wheat. Commercial exploitation of the minerals began in the late 70s and early 80s with the mineral being exported worldwide. The Greek deposit is still operated commercially, although the world's largest commercially operated reserves are in Turkey.

## Uses

Its most common industrial use is as a mixture with [huntite](/source/Huntite) as a [flame retardant](/source/Flame_retardant) or [fire retardant](/source/Fire_retardant) additive for [polymers](/source/Polymers).[11][12][13] Hydromagnesite decomposes endothermically,[5][6] giving off water and carbon dioxide, leaving a magnesium oxide residue. The initial decomposition begins at about 220 °C making it ideal for use as a filler in polymers and giving it certain advantages over the most commonly used fire retardant, [aluminium hydroxide](/source/Aluminium_hydroxide).[14] Syntheic hydromagnesite is known as [light magnesium carbonate](/source/Magnesium_carbonate) due to its low [bulk density](/source/Bulk_density).

## Thermal decomposition

Hydromagnesite thermally decomposes in three stages releasing water and carbon dioxide.[5][6]

The first stage starting at about 220 °C, is the release of the four molecules of water of crystallisation. This is followed at about 330 °C by the decomposition of the hydroxide ion to a further molecule of water. Finally, at about 350 °C carbon dioxide begins to be released. The release of the carbon dioxide can be further broken down into two stages depending on the rate of heating.[6]

## References

1. **[^](#cite_ref-1)** Warr, L.N. (2021). ["IMA–CNMNC approved mineral symbols"](https://doi.org/10.1180%2Fmgm.2021.43). *Mineralogical Magazine*. **85** (3): 291–320. [Bibcode](/source/Bibcode_(identifier)):[2021MinM...85..291W](https://ui.adsabs.harvard.edu/abs/2021MinM...85..291W). [doi](/source/Doi_(identifier)):[10.1180/mgm.2021.43](https://doi.org/10.1180%2Fmgm.2021.43). [S2CID](/source/S2CID_(identifier)) [235729616](https://api.semanticscholar.org/CorpusID:235729616).

1. ^ [***a***](#cite_ref-Handbook_2-0) [***b***](#cite_ref-Handbook_2-1) [Handbook of Mineralogy](http://rruff.geo.arizona.edu/doclib/hom/hydromagnesite.pdf)

1. ^ [***a***](#cite_ref-Webmin_3-0) [***b***](#cite_ref-Webmin_3-1) [Webmineral data](http://www.webmineral.com/data/Hydromagnesite.shtml)

1. **[^](#cite_ref-Mindat_4-0)** [Mindat](http://www.mindat.org/show.php?id=1979&ld=1#themap)

1. ^ [***a***](#cite_ref-Rev1_5-0) [***b***](#cite_ref-Rev1_5-1) [***c***](#cite_ref-Rev1_5-2) Hollingbery, LA; Hull TR (2010). ["The Thermal Decomposition of Huntite and Hydromagnesite - A Review"](http://clok.uclan.ac.uk/1139/). *Thermochimica Acta*. **509** (1–2): 1–11. [doi](/source/Doi_(identifier)):[10.1016/j.tca.2010.06.012](https://doi.org/10.1016%2Fj.tca.2010.06.012).

1. ^ [***a***](#cite_ref-Therm1_6-0) [***b***](#cite_ref-Therm1_6-1) [***c***](#cite_ref-Therm1_6-2) [***d***](#cite_ref-Therm1_6-3) Hollingbery, LA; Hull TR (2012). ["The Thermal Decomposition of Natural Mixtures of Huntite and Hydromagnesite"](http://clok.uclan.ac.uk/3414). *Thermochimica Acta*. **528**: 45–52. [Bibcode](/source/Bibcode_(identifier)):[2012TcAc..528...45H](https://ui.adsabs.harvard.edu/abs/2012TcAc..528...45H). [doi](/source/Doi_(identifier)):[10.1016/j.tca.2011.11.002](https://doi.org/10.1016%2Fj.tca.2011.11.002).

1. **[^](#cite_ref-7)** Braithwaite, C.; Zedef, Veysel (1996). "Living hydromagnesite stromatolites from Turkey". *Sedimentary Geology*. **106** (3–4): 309. [Bibcode](/source/Bibcode_(identifier)):[1996SedG..106..309B](https://ui.adsabs.harvard.edu/abs/1996SedG..106..309B). [doi](/source/Doi_(identifier)):[10.1016/S0037-0738(96)00073-5](https://doi.org/10.1016%2FS0037-0738%2896%2900073-5).

1. ^ [***a***](#cite_ref-sciencedirect.com_8-0) [***b***](#cite_ref-sciencedirect.com_8-1) Power, I.M.; Wilson, S.A.; Thom, J.M.; Dipple, G.M.; Gabites, J.E.; Southam, G. (2009). "The hydromagnesite playas of Atlin, British Columbia, Canada: A biogeochemical model for CO2 sequestration". *Chemical Geology*. **206** (3–4): 302–316. [Bibcode](/source/Bibcode_(identifier)):[2009ChGeo.260..286P](https://ui.adsabs.harvard.edu/abs/2009ChGeo.260..286P). [doi](/source/Doi_(identifier)):[10.1016/j.chemgeo.2009.01.012](https://doi.org/10.1016%2Fj.chemgeo.2009.01.012). [S2CID](/source/S2CID_(identifier)) [128900805](https://api.semanticscholar.org/CorpusID:128900805).

1. **[^](#cite_ref-9)** R. W. Renaut, *Recent Mamgnesite-Hydromagnesite sedimesntation in Playa Basins of the Caribou Plateau*, ["Archived copy"](https://web.archive.org/web/20041122123229/http://www.em.gov.bc.ca/DL/GSBPubs/GeoFldWk/1990/279-288-renaut.pdf) (PDF). Archived from [the original](http://www.em.gov.bc.ca/DL/GSBPubs/GeoFldWk/1990/279-288-renaut.pdf) (PDF) on 2004-11-22. Retrieved 2009-08-13.{{[cite web](https://en.wikipedia.org/wiki/Template:Cite_web)}}: CS1 maint: archived copy as title ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_archived_copy_as_title)) British Columbia Geologic Survey

1. **[^](#cite_ref-10)** Georgiades, GN (1996). "Huntite-hydromagnesite production and applications". *Proceedings of the 12th Industrial Minerals Congress*: 57–60.

1. **[^](#cite_ref-Rev2_11-0)** Hollingbery, LA; Hull TR (2010). ["The Fire Retardant Behaviour of Huntite and Hydromagnesite - A Review"](http://clok.uclan.ac.uk/1432). *Polymer Degradation and Stability*. **95** (12): 2213–2225. [doi](/source/Doi_(identifier)):[10.1016/j.polymdegradstab.2010.08.019](https://doi.org/10.1016%2Fj.polymdegradstab.2010.08.019).

1. **[^](#cite_ref-Fire1_12-0)** Hollingbery, LA; Hull TR (2012). ["The Fire Retardant Effects Huntite in Natural Mixtures with Hydromagnesite"](http://clok.uclan.ac.uk/3420/). *Polymer Degradation and Stability*. **97** (4): 504–512. [doi](/source/Doi_(identifier)):[10.1016/j.polymdegradstab.2012.01.024](https://doi.org/10.1016%2Fj.polymdegradstab.2012.01.024).

1. **[^](#cite_ref-Fire2_13-0)** Hull, TR; Witlowski A; Hollingbery LA (2011). ["Fire Retardant Action of Mineral Fillers"](http://clok.uclan.ac.uk/2963). *Polymer Degradation and Stability*. **96** (8): 1462–1469. [doi](/source/Doi_(identifier)):[10.1016/j.polymdegradstab.2011.05.006](https://doi.org/10.1016%2Fj.polymdegradstab.2011.05.006). [S2CID](/source/S2CID_(identifier)) [96208830](https://api.semanticscholar.org/CorpusID:96208830).

1. **[^](#cite_ref-14)** Rothon. R., Particulate-Filled Polymer Composites, 2nd Edition, 2003

Wikimedia Commons has media related to [Hydromagnesite](https://commons.wikimedia.org/wiki/Category:Hydromagnesite).

 Radial sprays of glassy **hydromagnesite** needles are scattered on pastel-green [magnesite](/source/Magnesite) (coloured by nickel impurities) with an unusual knobby/bubbly/drusy form. The specimen is from the Cedar Hill Quarry, [Fulton Township, Lancaster County, Pennsylvania](/source/Fulton_Township%2C_Lancaster_County%2C_Pennsylvania). Size: 7.3 x 5.5 x 3.1 cm.

---
Adapted from the Wikipedia article [Hydromagnesite](https://en.wikipedia.org/wiki/Hydromagnesite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Hydromagnesite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.