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Category Carbonate mineral
(repeating unit)
Strunz classification 05.AB.25
Dana classification
Crystal symmetry Trigonal trapezohedral
H-M symbol (3 2)
Space group: R 32
Unit cell a = 9.505 Å, c = 7.821 Å; Z=3
Formula mass 353
Color White, lemon white
Crystal habit Platy crystals; compact chalklike masses
Crystal system Trigonal
Fracture Subconchoidal
Tenacity Brittle
Mohs scale hardness 1-2
Luster Earthy (dull)
Streak White
Diaphaneity Translucent
Specific gravity 2.696
Optical properties Uniaxial (–)
Refractive index nω = 1.622 nε = 1.615
References [1][2][3]

Huntite is a carbonate mineral with the chemical formula Mg3Ca(CO3)4.[3] Huntite crystallizes in the trigonal system and typically occurs as platy crystals and powdery masses.


In 1953 a paper by George Faust[4] announced the discovery of a new carbonate mineral found in Currant Creek, Nevada (USA). Faust acknowledged that the mineral probably had been discovered previously, but had been misidentified as impure magnesite by W. E. Ford in 1917. Faust named the new mineral "huntite" in honour of his former teacher, Walter Frederick Hunt (1882–1975)[14] , Professor of Petrology at the University of Michigan.[5] Faust carried out analyses of the mineral, and found amongst others that in differential thermal analysis huntite showed two endothermic peaks, which could be attributed to the dissociation of MgCO3 and CaCO3 respectively. Chemical analyses showed huntite to consist of Mg3Ca(CO3)4.


Huntite often occurs in combination with other Mg/Ca carbonates such as dolomite, magnesite, and hydromagnesite. Large deposits of huntite occur in Turkey and Greece and these are commercially exploited because of its fire retardant properties. Huntite thermally decomposes over a temperature range of about 450–800 °C, releasing carbon dioxide and leaving a residue of magnesium and calcium oxides.[6][7][8]


Huntite has been found in a variety of environments. For example it occurs in the modern carbonate sediments of the tidal flats bordering the Persian Gulf,[9] in seasonal salt lakes of Turkey,[10][11][12][13] in various playa lakes of British Columbia (Canada),[14] in lacustrine deposits of Greece [15] and in modern sabkha sediments in Tunisia.[16][17]

Caves seem to be well suited for the low-temperature formation of huntite. For example it has been reported from the caves of the Carlsbad Caverns National Park, New Mexico (USA);[18][19][20] in the Castleguard Cave (Alberta, Canada);[21] in the Grotte de la Clamouse, France;[22][23] in various caves of the Transvaal Province of South Africa;[24] in the Jenolan Caves, Australia;[25] and in the Castañar Cave near Cáceres, Spain.[26] [27]


Huntite has been synthesized by Biedl & Preisinger (1962)[28] in experiments conducted at 100 °C and 3.2 bar CO2 pressure, and Hopkinson et al. (2012)[29] synthesized the mineral at 52 °C by reacting magnesium calcite with nesquehonite MgCO3.3 H2O. Oomori et al. (1983)[30] claimed laboratory synthesis of huntite at 33 °C when adding a sodium carbonate solution to concentrated sea water saturated with calcium bicarbonate. The precipitation of huntite at room temperature and atmospheric pressure was also noted by Zaitseva et al. (2006).[31] In laboratory experiments originally intended to synthesize magnesium calcite, cultures Microcoleus chtonoplastes (cyanobacteria) were added to sea water brine. After 10 months of continuously shaking the samples Zaitseva et al. (2006) found huntite, magnesite, and aragonite.


Huntite, dolomite and magnesite appear to be so very closely related, that a genetic relationship seems to be implied.[32] In a number of instances all three carbonates are found in close association; for example Faust (1953) described huntite occurring together with dolomite and magnesite (amongst other minerals); Carpenter (1961) [33] found huntite associated with aragonite, magnesium calcite and dolomite; Larrabee (1969) [34] reported on huntite together with (amongst many others) aragonite, calcite, dolomite and magnesite in serpentinite on a weathered dunite rock. A weathered basalt in Australia was found to contain huntite in association with magnesite (Cole & Lancucki, 1975 [35]). Huntite together with magnesite was found by Calvo et al. (1995) [36] in lake sediments of Northern Greece. Huntite in combination with magnesite occurs in a weathered serpentinite near Hrubšice, Czech Republic according to Němec (1981) [37] According to the mineral and locations database of "" huntite, together with aragonite, calcite, dolomite and magnesite can be found in the "U Pustého Mlýna" quarry near Hrubšice, Czech Republic.[15]

Industrial use[edit]

The most common industrial use of huntite is as a natural mixture with hydromagnesite as a flame retardant or fire retardant additive for polymers.[38][39][40] The heat of a fire will cause huntite to decompose releasing carbon dioxide into the flames. This helps to slow the spread of the fire. The release of carbon dioxide is endothermic, meaning that it takes in heat, this action helps to cool the burning material, again slowing the spread of the fire. These types of mixtures are used as alternatives to the more commonly used aluminium hydroxide.


A mineral with exactly the same composition as that of huntite has been known for more than 200 years; for example John (1812) [41] and Stromeyer (1812) [42] described it as having a chemical composition of CaCO3 : MgCO3 = 1 : 3 . In those days the mineral was known as conite (in German: Konit); a name given to it by Retzius (1798).[43] However, there is a serious problem concerning the exact location where the mineral conite can be found. Originally Retzius (1798) had found the new carbonate in a mineral collection, and had recognized it as a new species because it was harder than any of the known carbonates (even so hard, that it would spark when struck with steel). No indication was given as to the site where this conite originally had been found. A number of papers describing conite are known, but the mystery remains as to the exact location where it can be found. Ludwig (1804) [44] stated that the sample of conite studied by him, came "from Iceland". Leonhard (1805) [45] wrote that the conite he had analyzed came "from Scandinavia". Somewhat more exact was Stromeyer (1812), who claimed that his sample of conite had been found near the village of Frankenhayn, on the eastern slope of the Hoher Meissner (near Kassel, Germany). However, this conite had been found as a loose boulder, and no outcrop of the new mineral was mentioned. Blum (1833) [46] summed up how conite could be found in mines near Freiberg (Germany), as boulders on the slopes of Mount Meissner (Germany) and on Iceland. Hirzel (1849) [47] repeated that conite could be found on the eastern slope of Mount Meissner, and Schrauf (1882)[48] reported the mineral from the magnesite deposits on the borders of the Schöninger Bach at Křemže (near Budweis, Czech Republic). Because of the absence of a type locality for the mineral conite, historical priority of its description over that of huntite cannot be claimed.


  1. ^ Handbook of Mineralogy: Huntite
  2. ^ Huntite on
  3. ^ a b Huntite on Webmineral
  4. ^ Faust, GT (1953). "Huntite A New Mineral". American Mineralogist 38: 4–24. [1]
  5. ^ Ramsdell, LS (1958). "Presentation of the Roebling Medal to Walter F Hunt". American Mineralogist 43: 334–335. 
  6. ^ Ozao, R; Otsuka, R. (1985). "Thermoanalytical Investigation of Huntite". Thermochimica Acta 86: 45–58. doi:10.1016/0040-6031(85)87032-5. 
  7. ^ Hollingbery, LA; Hull TR (2010). "The Thermal Decomposition of Huntite and Hydromagnesite - A Review". Thermochimica Acta 509 (1-2): 1–11. doi:10.1016/j.tca.2010.06.012. 
  8. ^ Hollingbery, LA; Hull TR (2012). "The Thermal Decomposition of Natural Mixtures of Huntite and Hydromagnesite". Thermochimica Acta 528: 45–52. doi:10.1016/j.tca.2011.11.002. 
  9. ^ Kinsman, D. J. J. (1967): Huntite from a carbonate - evaporite environment. American Mineralogist, vol.52, pp.1332-1340. [2]
  10. ^ Irion, G. & Müller, G. (1968): Huntite, dolomite, magnesite and polyhalite of Recent age from Tuz Gölü, Turkey. Nature, vol.220, pp.1309-1310.
  11. ^ Irion, G. (1970): Mineralogisch-sedimentpetrographische und geochemische Untersuchungen am Tuz Gölü (Salzsee). Chemie der Erde, vol.29, pp.163-226.
  12. ^ Camur, M. Z. & Mutlu, H. (1996): Major-ion geochemistry and mineralogy of the Salt-Lake (Tuz Gölü) basin, Turkey. Chemical Geology, vol.127, pp.313-329.
  13. ^ Mutlu, H.; Kadir, S. & Akbulut, A. (1999): Mineralogy and water chemistry of the Lake Acigöl, Denizli, Turkey. Carbonates and Evaporites, vol.14, pp.191-199.
  14. ^ Renaut, R. W. (1990): Recent carbonate sedimentation and brine evolution in the saline lake basins of the Cariboo Plateau, British Columbia, Canada. pp.67-81, in: Comin, F. A. & Northcote, T. G. (eds.): Saline Lakes. Kluwer, Dordrecht.
  15. ^ Wetzenstein, W. (1974): Sedimentpetrographische Untersuchungen an limnischen Magnesit - Huntitlagerstätten im Plio-Pleistozän des Serviabeckens / Nordgriechenland. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, 1974, pp.625-642.
  16. ^ Perthuisot, J. P. (1971): Présence de magnésite et de huntite dans le sebkha el Melah de Zarzis. Comptes Rendus des séances de l'Academie des Sciences (Paris), Sér.D, vol.272, pp.185-188. [3]
  17. ^ Perthuisot, J. P. (1974): Les dépôts salins de la sebkha El Melah de Zarzis: Conditions et modalités de la sédimentation évaporitique. Revue de la geographie physique et de géologie dynamique, vol.16, pp.177-187.
  18. ^ Thrailkill, J. (1971): Carbonate deposition in Carlsbad caverns. Journal of Geology, vol.79, pp.683-695.
  19. ^ Hill, C. A. (1973): Huntite flowstone in Carlsbad Caverns, New Mexico. Science, vol.181, pp.158-159.
  20. ^ Gonzalez, L. A. & Lohmann, K. C. (1988): Controls on mineralogy and composition of spelean carbonates: Carlsbad Caverns, New Mexico. pp.81-101, in: James, N. P. & Choquette, P. W. (eds.): Paleokarst. Springer, New York, 416 p.
  21. ^ Harmon, R. S.; Atkinson, T. C. & Atkinson, J. L. (1983): The Mineralogy of Castleguard Cave, Columbia Icefields, Alberta, Canada]. Arctic and Alpine Research, vol.15, pp.503-522.
  22. ^ Baron, G.; Caillère, S.; Lagrange, R. & Pobeguin, T. (1957): Sur la présence de huntite dans une grotte de l'Hérault (la Clamouse). Comptes Rendus hebdomadaires des séances de l'Académie des Sciences (Paris), vol.245, pp.92-94. [4]
  23. ^ Fischbeck, R. (1976): Mineralogie und Geochemie carbonatischer Ablagerungen in europäischen Höhlen - ein Beitrag zur Bildung und Diagenese von Speleothemen. Neues Jahrbuch für Mineralogie, Abhandlungen, vol.126, pp.269-291.
  24. ^ Martini, J. & Kavalieris, I. (1978): Mineralogy of the Transvaal caves. Transactions of the Geological Society of South Africa, vol.81, pp.47-54.
  25. ^ Pogson, R. E.; Osborne, R. E. & Colchester, D. M. (2001): Minerals of the Jenolan Caves - geosphere meets biosphere. Journal and Proceedings of the Royal Society of New South Wales, vol.134, p.111. [5]
  26. ^ Alonso-Zarza, A. M.; Martín-Pérez, A.; Gil-Peña, I.; Martínez-Flores, E. & Muñoz-Barco, P. (2005): Formacíon de dolomita y huntita en depósitos de moon-milk en la Cueva de Castañar de Ibo (Cáceras). Geogaceta, July 2005, no.38, pp.247-250. [6]
  27. ^ Alonso-Zarza, A. M. & Martín-Pérez, A. (2008): Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments, Castañar Cave, Spain. Sedimentary Geology, vol.205, pp.160-164.
  28. ^ Biedl, A. & Preisinger, A. (1962): Synthese von Huntit, Mg3Ca(CO3)4. Anzeiger der mathematisch-naturwissenschaftliche Klasse, Österreichische Akademie der Wissenschaften (Wien), 1962, No.10, pp.148-149.
  29. ^ Hopkinson, L.; Kristova, P.; Rutt, K. & Cressey, G. (2012): Phase transitions in the system MgO - CO2 - H2O during CO2 degassing of Mg-bearing solutions. Geochimica et Cosmochimica Acta, vol.76, pp.1-13.
  30. ^ Oomori, T.; Kaneshima, K.; Taira, T. & Kitano, Y. (1983): Synthetic studies of protodolomite from brine waters. Geochemical Journal, vol.17, pp.147-152.
  31. ^ Zaitseva, L. V.; Orleanskii, V. K.; Gerasimenko, M. & Ushatinskaya, G. T. (2006): The role of cyanobacteria in crystallization of magnesium calcites. Paleontological Journal, vol.40, pp.125-133.
  32. ^ Müller, G.; Irion, G. & Förstner, U. (1972): Formation and diagenesis of inorganic Ca-Mg carbonates in the lacustrine environment. Die Naturwissenschaften, vol.59, pp.158-164.
  33. ^ Carpenter, A. B. (1961): Mineral assemblage magnesium calcite - aragonite - huntite at Crestmore, California. Geological Society of America, Abstracts for 1961, p.146.
  34. ^ Larrabee, D. M. (1969) Serpentinite and rodingite in the Hunting Hill Quarry, Montgomery County, Maryland. U.S. Geological Survey Bulletin, no.1283, 34 p. [7]
  35. ^ Cole, W. F. & Lancucki, C. J. (1975): Huntite, from Deer Park, Victoria, Australia. American Mineralogist, vol.60, pp.1130-1131. [8]
  36. ^ Calvo, J. P.; Stamatakis, M. G. & Magganas, A. C. (1955): Clastic huntite in Upper Neogene formations of the Kozani Basin, Macedonia, Northern Greece. Journal of Sedimentary Research, vol.A65, pp.627-632.
  37. ^ Němec, D. (1981): Huntit ze serpentinitové oblasti u Hrubšic na západni Moravě (Huntite from the serpentinite area at Hrubšice, Western Moravia - English summary). Časopis pro mineralogii a geologii, vol.26, pp.75-78.
  38. ^ Hollingbery, LA; Hull TR (2010). "The Fire Retardant Behaviour of Huntite and Hydromagnesite - A Review". Polymer Degradation and Stability 95 (12): 2213–2225. doi:10.1016/j.polymdegradstab.2010.08.019. 
  39. ^ Hollingbery, LA; Hull TR (2012). "The Fire Retardant Effects of Huntite in Natural Mixtures with Hydromagnesite". Polymer Degradation and Stability 97 (4): 504–512. doi:10.1016/j.polymdegradstab.2012.01.024. 
  40. ^ Hull, TR; Witkowski A; Hollingbery LA (2011). "Fire Retardant Action of Mineral Fillers". Polymer Degradation and Stability 96 (8): 1462–1469. doi:10.1016/j.polymdegradstab.2011.05.006. 
  41. ^ John, D. (1812): Chemische Analyse des Conits aus der Gegend des Meisseners. Journal für Chemie und Physik, vol.5, pp.13-18. [9]
  42. ^ Stromeyer, F. (1812): Analyse des sogenannten Konits vom Meissner. Annalen der Physik, vol.41, pp.336-338. [10]
  43. ^ Retzius, A. J. (1798): Versuch einer Aufstellung des Mineralreiches. S. L. Crusius, Leipzig, 376 p.
  44. ^ Ludwig, C. F. (1804): Handbuch der Mineralogie nach A. G. Werner. S. L. Crusius, Leipzig, Theil 2 = 226 p. [11]
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  46. ^ Blum, J. R. (1833): Lehrbuch der Oryktognosie. Schweizerbart, Stuttgart, 509 p. [13]
  47. ^ Hirzel, H. (1849): Analyse des Konits von Frankenheyn am östlichen Abhange des Meissners. Archiv der Pharmacie, vol.109, pp.154-156.
  48. ^ Schrauf, A. (1882): Beiträge zur Kenntnis des Associationskreises des Magnesiasilicate. Zeitschrift für Krystallographie und Mineralogie, vol.6, pp.321-388.