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Chlorite Group

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About Chlorite GroupHide

2 - 2½
Specific Gravity:
2.6 - 3.3
Crystal System:
A group of mostly monoclinic (also triclinic or orthorhombic) micaceous phyllosilicate minerals with a structure consisting of T-O-T layers with two layers having their silicate tetrahedral apices pointing towards each other, separated by an interlayer that may be simple octahedrally coordinated cations or which may be a brucite-*like* layer of two sheets of closely packed OH groups with the interstices between sheets providing the octahedral coordination site; the T-O-T layers and interlayer are bonded by electrostatic and hydrogen bonding forces; as the "a" and "b" directions of the T-O-T layer may be oriented to the interlayer "a" and "b" directions in twelve different stacking sequences, resulting in twelve different polytype possibilities (not all of which have been found in Nature yet for each species).

The general formula may be stated A5-6T4Z18, where A = Al, Fe2+, Fe3+, Li, Mg, Mn, or Ni, while T = Al, Fe3+, Si, or a combination of them, and Z = O and/or OH.

The most common species in the chlorite group are clinochlore and chamosite.

The Árkai index (ÁI; Árkai, 1991) is an index for the estimation of a very low metamorphic grade in rocks, based on the evolution of chlorite. It is often used to complement the Kübler index (KI), earlier called the 'illite crystallinity' for the characterisation of pelites, and can also be applied in metabasites.

Pronounciation of Chlorite GroupHide

PlayRecorded byCountry
Jolyon & Katya RalphUnited Kingdom

Physical Properties of Chlorite GroupHide

2 - 2½ on Mohs scale
2.6 - 3.3 g/cm3 (Measured)    

Age distributionHide

Recorded ages:
Paleoproterozoic to Neogene : 2211 Ma to 15.7 ± 0.2 Ma - based on 7 recorded ages.

Crystallography of Chlorite GroupHide

Crystal System:

Synonyms of Chlorite GroupHide

Other Language Names for Chlorite GroupHide

Simplified Chinese:绿泥石族

Varieties of Chlorite GroupHide

BrunsvigiteA chloritic mineral.
Originally described from Gabbro Quarry (Bärenstein Quarry), Bad Harzburg, Harz Mts, Lower Saxony, Germany.
PrasoliteA soft leek-green fibrous mineral from Kilpatrick Hills, Scotland. An aluminosilicate of Mg and Fe, probably a variety of chlorite.

Relationship of Chlorite Group to other SpeciesHide

Group Members:
Baileychlore (Zn,Fe2+,Al,Mg)6(Si,Al)4O10(OH)8Tric. 1
Borocookeite Li1+3xAl4-x(BSi3O10)(OH)8
Chamosite (Fe2+,Mg,Al,Fe3+)6(Si,Al)4O10(OH,O)8Mon.
Clinochlore Mg5Al(AlSi3O10)(OH)8Mon. 2/m : B2/m
Cookeite (Al2Li)Al2(AlSi3O10)(OH)8Mon. 2/m
Donbassite Al4.33(AlSi3O10)(OH)8Mon. 2 : B2
Franklinfurnaceite Ca2Fe3+Mn2+3Mn3+(Zn2Si2O10)(OH)8Mon. 2 : B2
Glagolevite Na(Mg,Al)6(AlSi3O10)(OH,O)8Tric. 1 : P1
Gonyerite (Mn2+,Mg)5Fe3+(Fe3+Si3O10)(OH)8
Nimite (Ni,Mg,Al)6((Si,Al)4O10)(OH)8Mon.
Orthochamosite (Fe2+,Mg,Fe3+)5Al(AlSi3O10)(OH,O)8
Pennantite Mn2+5Al(AlSi3O10)(OH)8Tric.
Sudoite Mg2Al3(Si3Al)O10)(OH)8Mon.

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Chlorite Group in petrologyHide

References for Chlorite GroupHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Hey, M. H. (1954): A new review of chlorites. Mineral. Mag. 30, 277-292.
Dodge, F.C.W. (1973): Chlorites from the granitic rocks of the central Sierra Nevada batholith. Mineralogical Magazine, 39, 58-64.
Post, J.L. and Janke, N.C. (1974): Properties of “swelling chlorite” in some Mesozoic formations of California. Clays and Clay Minerals, 22, 67-77.
Hazen, R.M. and Finger, L.W. (1978): The crystal structures and compressibilities of layer minerals at high pressure. II. Phlogopite and chlorite. American Mineralogist, 63, 293-296.
S. Durovic, K. Dornberger-Schiff and Z. Weiss (1983): Chlorite polytypism. I. OD interpretation and polytype symbolism of chlorite structures. Acta Crystallogr. B39, 547-552.
Spinnler, G.E. (1985): HRTEM study of antigorite, pyroxene-serpentine reactions and chlorite, 248 p. Ph.D. Thesis, Arizona State University, Tempe, Arizona.
Schreyer, W., Fransolet, A.M., and Abraham, K. (1986): A miscibility gap in trioctahedral Mn-Mg-Fe chlorites: evidence from the Lienne Valley manganese deposit, Ardennes, Belgium. Contributions to Mineralogy and Petrology, 94, 333-342.
Bailey, S. W. (1988): Chlorites: Structures and crystal chemistry. Reviews in Mineralogy 19, 347-403.
Wiewiora, A. & Weiss, Z. (1990): Crystallochemical classifications of phyllosilicates based on the unified system of projection of chemical composition: II. The chlorite group. Clay Minerals 25, 83-92.
Árkai, P. (1991): Chlorite crystallinity: an empirical approach and correlation with illite crystallinity, coal rank and mineral facies as exemplified by Palaeozoic and Mesozoic rocks of northeast Hungary. J. Metamorphic Geology 9, 723-734.
Hillier, S. and Velde, B. (1991): Octahedral occupancy and the chemical composition of diagenetic (low-temperature) chlorite. Clay Minerals, 26, 149-168.
De Caritat, P., Hutcheon, I. & Walshe, J.E. (1993): Chlorite geothermometry: a review. Clays and Clay Minerals, 41, 219-239.
Árkai, P. and Ghabrial, D. (1997): Chlorite crystallinity as an indicator of metamorphic grade of low-temperature meta-igneous rocks; a case study from the Bükk Mountains, Northeast Hungary. Clay Minerals, 32, 205-222.
Li, G., Peacor, D.R., and Essene, E.J. (1998) The formation of sulfides during alteration of biotite to chlorite-corrensite. Clays and Clay Minerals, 46, 649-657.
Lougear, A., M. Grodzicki, C. Bertoldi, A.X. Trautwein, K. Steiner, and G. Amthauer (2000): Mössbauer and molecular orbital study of chlorites. Physica and Chemistry of Minerals, 27, 258-269.
Bertoldi, C., Benisek, A., Cemic, L., and Dachs, E. (2001): The heat capacity of two natural chlorite group minerals derived from differential scanning calorimetry. Physics and Chemistry of Minerals, 28, 332-336.

Internet Links for Chlorite GroupHide

Significant localities for Chlorite GroupHide

Showing 25 significant localities out of 15,949 recorded on mindat.org.

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
  • Queensland
    • Mareeba Shire
      • Mungana
[Baileychlore] AM 73 (1988), 135; HB2/1 (1995)
Czech Republic
  • Central Bohemian Region
    • Kutná Hora (Kuttenberg)
[Orthochamosite] Am Min 43 (1958), 792
  • Baden-Württemberg
    • Stuttgart
      • Plochingen
        • Lützelbach
[Sudoite] Amer.Min.(1963) 48, 213
  • Attica
    • East Attica
      • Lavreotiki
        • Lavrion District Mines
          • Agios Konstantinos [St Constantine] (Kamariza)
            • Kamariza Mines (Kamareza Mines)
[Baileychlore] LAPIS 2010 7/8, p. 14 (Kristalldruse ad); Rieck, B. (2012): Neue Minerale aus dem Lagerstätten-Bezirk Lavrion/Griechenland und den Kalahari Mangan Feldern/Republik Südafrika. PhD Thesis (unpubl.), University of Vienna, 183 pp. (in German); Kolitsch, U., Rieck, B., Brandstätter, F., Schreiber, F., Fabritz, K. H., Blaß, G. & Gröbner, J. (2014): Neufunde aus dem altem Bergbau und den Schlacken von Lavrion (I). Mineralien-Welt 25 (1), 60-75 (in German).
  • Lower Silesia
    • Świdnica
[Chamosite] Dana, E., 1892, System of Mineralogy (chemical analysis)
[Chamosite] Tomas Praszkier
  • Murmansk Oblast
    • Kovdor Massif
[Glagolevite] M. V. Seredkin et al.: Zap. Vses. Min. Obshch.:132(1), 67-75 (2003)
  • Zabaykalsky Krai
    • Chitinskaya Oblast
      • Krasnyi Chikoy
        • Malkhan pegmatite field (Malchan; "Malechansk")
[Borocookeite] American Mineralogist, 88, 830-836.; International Geological Congress (2008) MRD-06 The Sosedka gem tourmaline-rich mine: Emplacement of extremely chemically heterogeneous pegmatite-forming medium; Zagorsky, V. Y. (2012). Mineralogy of pockets of the Malkhan tourmaline deposit (< i> Transbaikalia): feldspars of the Sosedka vein. Russian Geology and Geophysics, 53(6), 522-534
South Africa
  • Mpumalanga
    • Ehlanzeni District
      • Barberton
        • Bon Accord
[Nimite] American Mineralogist (1969): 54: 1739; O'Driscoll, B., Clay, P. L., Cawthorn, R. G., Lenaz, D., Adetunji, J., & Kronz, A. (2014). Trevorite: Ni-rich spinel formed by metasomatism and desulfurization processes at Bon Accord, South Africa?. Mineralogical Magazine, 78(1), 145-163.
  • Värmland
    • Filipstad
[Gonyerite] Amer.Min.(1955) 40, 1090-1094; Nysten, P., Holtstam, D. and Jonsson, E. (1999) The Långban minerals. In Långban - The mines,their minerals, geology and explorers (D. Holtstam and J. Langhof, eds.), Swedish Museum of Natural History and Raster Förlag, Stockholm & Chr. Weise Verlag, Munich, pp. 89-183.
  • Wallis (Valais)
    • Chamoson
[Chamosite] Berthier, P. (1820): Annales des Mines 5, 393-396; Delaloye, M. (1962): Chamosite of Chamoson, Valais. Schweizerische Mineralogische und Petrographische Mitteilungen 42, 644.
  • Wales
    • Gwynedd
      • Lleyn Peninsula
        • Llanfaelrhys
          • Rhiw
[Pennantite] Campbell, et al (1946); Canadian Mineralogist:21(1983):545.; UK Journal of mines & Minerals, number 29 pp47-48; Am Min (1955) 40:32-40; W. Campbell Smith and F. A. Bannister (1948) Ganophyllite from the Benallt Mine, Rhiw, Carnarvonshire Mineralogical Magazine 28:343-352
  • Donetsk Oblast
[Donbassite] Lazarenko, E. K. (1940) Donbassites, a new group of minerals from the Donetz Basin. (in Russian) C. R. Acad. Sci. URSS, 28, 519-521.
  • California
    • Calaveras Co.
      • Valley Springs area
Jake Harper: Field work, 1990 - 2110.
  • Connecticut
    • Fairfield Co.
      • Trumbull
        • Long Hill
[Clinochlore] Shannon, Earl V. (1921b), Some Minerals from the Old Tungsten Mine at Long Hill in Trumbull, Connecticut. Proceedings U.S. National Museum: 58(2348): 469-482.; Januzzi, Ronald E. (1994): Mineral Data Book - Western Connecticut and Environs. Mineralogical Press, Danbury, Connecticut.
[Clinochlore] P Cristofono collection, 2008
    • Middlesex Co.
      • Haddam
        • Haddam Neck
[Cookeite] Mineralogical Record 23:19-28,80; Mineralogical Magazine 1902 13 : 97-121.; Rocks & Minerals (1995) 70:396-409; Earl Ingerson. American Mineralogist, Vol. 23, No. 4, April 1938, pp. 269-276
      • Portland
        • Collins Hill
          • Strickland pegmatite (Strickland-Cramer Quarry; Strickland-Cramer Mine; Strickland-Cramer Feldspar-Mica Quarries)
[Cookeite] Schooner, Richard. (1955): 90 Minerals from 1 Connecticut Hill. Rocks & Minerals: 30(7-8): 351-8.; Schooner, Richard. (1958): The Mineralogy of the Portland-East Hampton-Middletown-Haddam Area in Connecticut (With a few notes on Glastonbury and Marlborough). Published by Richard Schooner; Ralph Lieser of Pappy’s Beryl Shop, East Hampton; and Howard Pate of Fluorescent House, Branford, Connecticut.
  • Maine
    • Oxford Co.
      • Buckfield
[Cookeite] King, V. and Foord, E., 1994, Mineralogy of Maine.; Mineralogical Record 22:382
      • Hebron
[Cookeite] Brush (1866) Am J.. Sci 41:246 ; Penfield (1893) Am. J. Sci 3rd ser. 45:393; USGS Bull 445
      • Paris
[Cookeite] King, V. T. and Foord, E. E., 1994, Mineralogy of Maine, Descriptive Mineralogy, volume 1, Maine Geological Survey, Augusta, Maine, USA, pp. 418 + 88 plates.
  • New Hampshire
    • Coos Co.
      • Gorham
[Chamosite] A. Plante collection; R. Janules collection; A. Smith collection; et.al.
  • New Jersey
    • Sussex Co.
      • Franklin mining district
        • Franklin
[Franklinfurnaceite] Dunn, P.J., et al: Am. Min.:72:812-815 (1987); Dunn(1995):Pt4:493-494.
  • New York
    • Putnam Co.
      • Town of Southeast
        • Brewster
[Clinochlore] (Bridenbaugh, 1873) (Dana, J. D., 1874) (Januzzi, 1966, 1989) (Manchester, 1931) (Trainer, 1938) (Whitlock, 1903).
  • Pennsylvania
    • Chester Co.
      • Westtown Township
        • West Chester
[Clinochlore] Dana 6:1068; Rocks & Min.: 21:22.
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