Kaolinite /ˈkeɪəlɪˌnaɪt/ is a clay mineral, part of the
group of industrial minerals, with the chemical composition
Al2Si2O5(OH)4. It is a layered silicate mineral, with one tetrahedral
sheet of silica (SiO4) linked through oxygen atoms to one octahedral
sheet of alumina (AlO6) octahedra. Rocks that are rich in kaolinite
are known as kaolin /ˈkeɪəlɪn/ or china clay.
The name "kaolin" is derived from "Gaoling" (Chinese: 高嶺; pinyin:
Gāolǐng; literally: "High Ridge"), a Chinese village near Jingdezhen
in southeastern China's
Jiangxi Province. The name entered English
in 1727 from the French version of the word: kaolin, following
Francois Xavier d'Entrecolles's reports from Jingdezhen.
Kaolinite has a low shrink–swell capacity and a low cation-exchange
capacity (1–15 meq/100 g). It is a soft, earthy, usually white,
mineral (dioctahedral phyllosilicate clay), produced by the chemical
weathering of aluminium silicate minerals like feldspar. In many parts
of the world it is colored pink-orange-red by iron oxide, giving it a
distinct rust hue. Lighter concentrations yield white, yellow, or
light orange colors. Alternating layers are sometimes found, as at
Providence Canyon State Park
Providence Canyon State Park in Georgia, United States. Commercial
grades of kaolin are supplied and transported as dry powder, semi-dry
noodle or as liquid slurry.
1.2 Structural transformations
1.2.4 Platelet mullite
1.2.5 Needle mullite
3 Synthesis and genesis
3.1 Laboratory syntheses
4.2.1 United States
5 See also
6.2 General references
7 External links
The chemical formula for kaolinite as used in mineralogy is
Al2Si2O5(OH)4, however, in ceramics applications the formula is
typically written in terms of oxides, thus the formula for kaolinite
Kaolinite group clays undergo a series of phase transformations upon
thermal treatment in air at atmospheric pressure.
See also: Buell dryer
Below 100 °C (212 °F), exposure to dry air will slowly
remove liquid water from the kaolin. The end-state for this
transformation is referred to as "leather dry". Between 100 °C
and about 550 °C (1,022 °F), any remaining liquid water is
expelled from kaolinite. The end state for this transformation is
referred to as "bone dry". Throughout this temperature range, the
expulsion of water is reversible: if the kaolin is exposed to liquid
water, it will be reabsorbed and disintegrate into its fine
particulate form. Subsequent transformations are not reversible, and
represent permanent chemical changes.
Endothermic dehydration of kaolinite begins at 550–600 °C
producing disordered metakaolin, but continuous hydroxyl loss is
observed up to 900 °C (1,650 °F). Although
historically there was much disagreement concerning the nature of the
metakaolin phase, extensive research has led to a general consensus
that metakaolin is not a simple mixture of amorphous silica (SiO2) and
alumina (Al2O3), but rather a complex amorphous structure that retains
some longer-range order (but not strictly crystalline) due to stacking
of its hexagonal layers.
Al2Si2O5(OH)4 → Al2Si2O7 + 2 H2O.
Further heating to 925–950 °C converts metakaolin to an
aluminium-silicon spinel which is sometimes also referred to as a
gamma-alumina type structure:
2 Al2Si2O7 → Si3Al4O12 + SiO2.
Upon calcination above 1050 °C, the spinel phase nucleates and
transforms to platelet mullite and highly crystalline cristobalite:
3 Si3Al4O12 → 2 (3 Al2O3 + 2 SiO2) + 5 SiO2.
Finally, at 1400 °C the "needle" form of mullite appears,
offering substantial increases in structural strength and heat
resistance. This is a structural but not chemical transformation. See
stoneware for more information on this form.
Kaolinite is one of the most common minerals; it is mined, as kaolin,
in Malaysia, Pakistan, Vietnam, Brazil, Bulgaria, France, United
Kingdom, Iran, Germany, India, Australia, Korea, the People's Republic
of China, the Czech Republic, Spain, South Africa, and the United
Mantles of kaolinitic saprolite are common in Western and Northern
Europe. The ages of these mantles are
Mesozoic to Early Cenozoic.
Kaolinite clay occurs in abundance in soils that have formed from the
chemical weathering of rocks in hot, moist climates—for example in
tropical rainforest areas. Comparing soils along a gradient towards
progressively cooler or drier climates, the proportion of kaolinite
decreases, while the proportion of other clay minerals such as illite
(in cooler climates) or smectite (in drier climates) increases. Such
climatically-related differences in clay mineral content are often
used to infer changes in climates in the geological past, where
ancient soils have been buried and preserved.
In the Institut National pour l'Etude Agronomique au Congo Belge
(INEAC) classification system, soils in which the clay fraction is
predominantly kaolinite are called kaolisol (from kaolin and
In the US, the main kaolin deposits are found in central Georgia, on a
stretch of the
Atlantic Seaboard fall line between Augusta and Macon.
The deposits were formed between the late
Cretaceous and early
Paleogene, about 100 million to 45 million years ago, in sediments
derived from weathered igneous and metakaolin rocks. Kaolin
production in the US during 2011 was 5.5 million tonnes.
Paleocene–Eocene Thermal Maximum
Paleocene–Eocene Thermal Maximum sediments were enriched
with kaolinite from a detrital source due to denudation.
Synthesis and genesis
Difficulties are encountered when trying to explain kaolinite
formation under atmospheric conditions by extrapolation of
thermodynamic data from the more successful high-temperature syntheses
(as for example Meijer and Van der Plas, 1980 have pointed out).
La Iglesia and Van Oosterwijk-Gastuche (1978) thought that the
conditions under which kaolinite will nucleate can be deduced from
stability diagrams based as these are on dissolution data. Because of
a lack of convincing results in their own experiments, La Iglesia and
Van Oosterwijk-Gastuche (1978) had to conclude, however, that there
were other, still unknown, factors involved in the low-temperature
nucleation of kaolinite. Because of the observed very slow
crystallization rates of kaolinite from solution at room temperature
Fripiat and Herbillon (1971) postulated the existence of high
activation energies in the low-temperature nucleation of kaolinite.
At high temperatures, equilibrium thermodynamic models appear to be
satisfactory for the description of kaolinite dissolution and
nucleation, because the thermal energy suffices to overcome the energy
barriers involved in the nucleation process. The importance of
syntheses at ambient temperature and atmospheric pressure towards the
understanding of the mechanism involved in the nucleation of clay
minerals lies in overcoming these energy barriers. As indicated by
Caillère and Hénin (1962) the processes involved will have to be
studied in well-defined experiments, because it is virtually
impossible to isolate the factors involved by mere deduction from
complex natural physico-chemical systems such as the soil environment.
Fripiat and Herbillon (1971), in a review on the formation of
kaolinite, raised the fundamental question how a disordered material
(i.e., the amorphous fraction of tropical soils) could ever be
transformed into a corresponding ordered structure. This
transformation seems to take place in soils without major changes in
the environment, in a relatively short period of time and at ambient
temperature (and pressure).
Low-temperature synthesis of clay minerals (with kaolinite as an
example) has several aspects. In the first place the silicic acid to
be supplied to the growing crystal must be in a monomeric form, i.e.,
silica should be present in very dilute solution (Caillère et al.,
1957; Caillère and Hénin, 1962; Wey and Siffert, 1962;
Millot, 1970). In order to prevent the formation of amorphous
silica gels precipitating from supersaturated solutions without
reacting with the aluminium or magnesium cations to form crystalline
silicates, the silicic acid must be present in concentrations below
the maximum solubility of amorphous silica. The principle behind this
prerequisite can be found in structural chemistry: “Since the
polysilicate ions are not of uniform size, they cannot arrange
themselves along with the metal ions into a regular crystal lattice”
(Iler, 1955, p. 182).
The second aspect of the low-temperature synthesis of kaolinite is
that the aluminium cations must be hexacoordinated with respect to
oxygen (Caillère and Hénin, 1947; Caillère et al., 1953;
Hénin and Robichet, 1955). Gastuche et al. (1962), as well as
Caillère and Hénin (1962) have concluded, that only in those
instances when the aluminium hydroxide is in the form of gibbsite,
kaolinite can ever be formed. If not, the precipitate formed will be a
“mixed alumino-silicic gel” (as Millot, 1970, p. 343 put it).
If this would be the only requirement, large amounts of kaolinite
could be harvested simply by adding gibbsite powder to a silica
solution. Undoubtedly a marked degree of sorption of the silica in
solution by the gibbsite surfaces will take place, but, as stated
before, mere adsorption does not create the layer lattice typical of
The third aspect is that these two initial components must be
incorporated into one and the same mixed crystal with a layer
structure. From the following equation (as given by Gastuche and
DeKimpe, 1962) for kaolinite formation
2 Al(OH)3 + 2 H4SiO4 → Si2O5.2 Al(OH)3 + 5 H2O
it can be seen, that five molecules of water must be removed from the
reaction for every molecule of kaolinite formed. Field evidence
illustrating the importance of the removal of water from the kaolinite
reaction has been supplied by Gastuche and DeKimpe (1962). While
studying soil formation on a basaltic rock in
Kivu (Zaïre), Gastuche
and DeKimpe noted how the occurrence of kaolinite depended on the
"degrée de drainage" of the area involved. A clear distinction was
found between areas with good drainage (i.e., areas with a marked
difference between wet and dry seasons) and those areas with poor
drainage (i.e., perennially swampy areas). Only in the areas with
distinct seasonal alternations between wet and dry conditions
kaolinite was found. The possible significance of alternating wet and
dry conditions on the transition of allophane into kaolinite has been
stressed by Tamura and Jackson (1953). The role of alternations
between wetting and drying on the formation of kaolinite has also been
noted by Moore (1964).
Syntheses of kaolinite at high temperatures (more than 100 °C
[212 °F]) are relatively well known. There are for example the
syntheses of Van Nieuwenberg and Pieters (1928); Noll (1934);
Noll (1936); Norton (1939); Roy and Osborn (1954); Roy
(1961); Hawkins and Roy (1962); Tomura et al. (1985);
Satokawa et al. (1994) and Huertas et al. (1999). Relatively
few low-temperature syntheses have become known (cf. Brindley and
DeKimpe (1961); DeKimpe (1969); Bogatyrev et al. (1997)).
Laboratory syntheses of kaolinite at room temperature and atmospheric
pressure have been described by DeKimpe et al. (1961). From those
tests the role of periodicity becomes convincingly clear. For DeKimpe
et al. (1961) had used daily additions of alumina (as AlCl3. 6 H2O)
and silica (in the form of ethyl silicate) during at least two months.
In addition adjustments of the pH took place every day by way of
adding either hydrochloric acid or sodium hydroxide. Such daily
additions of Si and Al to the solution in combination with the daily
titrations with hydrochloric acid or sodium hydroxide during at least
60 days will have introduced the necessary element of periodicity.
Only now the actual role of what has been described as the “aging”
(Alterung) of amorphous alumino-silicates (as for example Harder,
1978 had noted) can be fully understood. For time as such is not
bringing about any change in a closed system at equilibrium, but a
series of alternations, of periodically changing conditions (by
definition taking place in an open system), will bring about the
low-temperature formation of more and more of the stable phase
kaolinite instead of (ill-defined) amorphous alumino-silicates.
The main use of the mineral kaolinite (about 50% of the time) is the
production of paper; its use ensures the gloss on some grades of
Kaolin is also known for its capabilities to induce and accelerate
blood clotting. In April 2008 the US Naval Medical Research Institute
announced the successful use of a kaolinite-derived aluminosilicate
infusion in traditional gauze, known commercially as QuikClot Combat
Gauze, which is still the hemostat of choice for all branches of
the US military.
Kaolin is used (or was used in the past):
in ceramics (it is the main component of porcelain)
as a light-diffusing material in white incandescent light bulbs
in 'pre-work' skin protection and barrier creams
in paint to extend the titanium dioxide (TiO2) white pigment and
modify gloss levels
for modifying the properties of rubber upon vulcanization
in adhesives to modify rheology
in organic farming as a spray applied to crops to deter insect damage,
and in the case of apples, to prevent sun scald
as whitewash in traditional stone masonry homes in Nepal (the most
common method is to paint the upper part with white kaolin clay and
the middle with red clay; the red clay may extend to the bottom, or
the bottom may be painted black)
as a filler in Edison Diamond Discs
As a filler to give bulk, or a coating to improve the surface in paper
as an indicator in radiological dating since kaolinite can contain
very small traces of uranium and thorium
to soothe an upset stomach, similar to the way parrots (and later,
South America originally used it (more recently,
industrially-produced kaolinite preparations were common for treatment
of diarrhea; the most common of these was kaopectate, which abandoned
the use of kaolin in favor of attapulgite and then (in the United
States) bismuth subsalicylate (the active ingredient in Pepto-Bismol))
for facial masks or soap ( known as "White Clay"), being especially
Ayurveda based herbal packs for
Acne prone skin.
as adsorbents in water and wastewater treatment
to induce blood clotting in diagnostic procedures, e.g. Kaolin
In its altered metakaolin form, as a pozzolan; when added to a
concrete mix, metakaolin accelerates the hydration of Portland cement
and takes part in the pozzolanic reaction with the portlandite formed
in the hydration of the main cement minerals (e.g. alite).
In its altered metakaolin form, as a base component for geopolymer
Humans sometimes eat kaolin for health or to suppress hunger, a
practice known as geophagy. Consumption is greater among women,
especially during pregnancy. This practice has also been observed
within a small population of African-American women in the Southern
United States, especially Georgia. There, the kaolin is called
white dirt, chalk or white clay.
People can be exposed to kaolin in the workplace by breathing in the
powder or from skin or eye contact.
Occupational Safety and Health Administration
Occupational Safety and Health Administration (OSHA) has set the
legal limit (permissible exposure limit) for kaolin exposure in the
workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory
exposure over an 8-hour workday. The National Institute for
Occupational Safety and Health (NIOSH) has set a recommended exposure
limit (REL) of 10 mg/m3 total exposure TWA 5 mg/m3
respiratory exposure over an 8-hour workday.
Kaolin Deposits of Charentes Basin, France
^ a b "
Kaolinite mineral information and data". MinDat.org. Retrieved
Kaolinite Mineral Data". WebMineral.com. Retrieved
^ a b
Kaolinite in the Handbook of Mineralogy
^ "kaolinite - definition of kaolinite in English from the Oxford
dictionary". OxfordDictionaries.com. Retrieved 2016-01-20.
Dictionary.com Unabridged. Random House.
^ Deer, W.A.; Howie, R.A.; Zussman, J. (1992). An introduction to the
rock-forming minerals (2 ed.). Harlow: Longman.
^ Pohl, Walter L. (2011). Economic geology: principles and
practice : metals, minerals, coal and hydrocarbons –
introduction to formation and sustainable exploitation of mineral
deposits. Chichester, West Sussex: Wiley-Blackwell. p. 331.
^ Schroeder, Paul (2003-12-12). "Kaolin". New Georgia Encyclopedia.
^ Harper, Douglas. "kaolin". Online Etymology Dictionary.
^ Handbook of Inorganic Compounds, Dale L. Perry, Taylor &
Francis, 2011, ISBN 978-1-4398-1461-1
^ a b Bellotto, M., Gualtieri, A., Artioli, G., and Clark, S.M.
(1995). "Kinetic study of the kaolinite-mullite reaction sequence.
Part I: kaolinite dehydroxylation". Phys. Chem. Minerals. 22 (4):
doi:10.1007/BF00202253. CS1 maint: Multiple names: authors list
^ Migoń, Piotr; Lidmar-Bergström, Karna (2002). "Deep weathering
through time in central and northwestern Europe: problems of dating
and interpretation of geological record". Catena. 49: 25–40.
^ Young, Anthony (1980). Tropical soils and soil survey. Cambridge
Geographical Studies. 9. CUP Archive. p. 132.
^ Paul A. Schroeder (December 2003). "Kaolin". New Georgia
^ Virta, Robert (2012). Mineral Commodity Summaries (PDF) (Technical
report). U.S. Geological Survey. pp. 44–45.
^ Thierry Adatte, Hassan Khozyem, Jorge E. Spangenberg, Bandana Samant
& Gerta Keller (2014). "Response of terrestrial environment to the
Paleocene-Eocene Thermal Maximum (PETM), new insights from India and
NE Spain". Rendiconti della Società Geologica Italiana.
doi:10.3301/ROL.2014.17. CS1 maint: Uses authors parameter (link)
^ Meijer, E. L. and Plas, L. van der (1980): Relative stabilities of
soil minerals. Mededelingen Landbouwhogeschool Wageningen, vol.80,
no.16, 18 p.
^ Iglesia, A. La and Van Oosterwyck-Gastuche, M. C. (1978): Kaolinite
synthesis. I. Crystallization conditions at low temperatures and
calculation of thermodynamic equilibria. Application to laboratory and
field observations. Clays and
Clay Minerals, vol.26, pp.397-408
^ Caillère, S. and Hénin, S. (1962): Vues ensemble sur le problème
de la synthèse des minéraux phylliteux à basse température.
Colloques Internationaux No.105, Centre National des Recherches
^ Fripiat, J. J. and Herbillon, A. J. (1971): Formation and
transformations of clay minerals in tropical soils. pp.15-24, in:
Soils and tropical weathering, Proceedings Bandung Symposium November
1969, Natural Resources Research, XI. Unesco, Paris, 149 p.
^ Caillère, S.; Hénin, S. and Esquevin, J. (1957): Synthèse des
minéraux argileux. Étude des réactions du silicate de sodium et des
cations. Bulletin du Groupe Français des Argiles, no.9.
^ Wey, R. and Siffert, B. (1961): Réactions de la silice
monomoléculaire en solutions avec les ions Al3+ et Mg2+ . Colloques
Internationaux No.105, Centre National des Recherches Scientifiques,
^ Millot, G. (1970): Geology of clays. Springer Verlag, New York, 429
^ Iler, R. K. (1955): The colloid chemistry of silica and silicates.
Cornell Univ. Press, Ithaca, N.Y., 324 p.
^ Caillère, S. and Hénin, S. (1947): Formation d’une phyllite du
type kaolinique par traitement d’une montmorillonite. Comptes Rendus
des Séances de l’Académie des Sciences (Paris), vol.224, pp.53-55.
^ Caillère, S.; Hénin, S. and Esquevin, J. (1953): Recherches sur la
synthèse des minéraux argileux. Bulletin de la Societé Française
de Minéralogie, vol.76, pp.300-314.
^ Hénin, S. and Robichet, O. (1954): Résultats obtenus au cours de
nouveaux essais de synthèse des minéraux argileux. Bulletin de la
Groupe Française des Argiles, vol.6, pp.19-22.
^ Gastuche, M. C.; Fripiat, J. J. and DeKimpe, C. (1962): La genèse
des minéraux argileux de la famille du kaolin. I. – Aspect
colloidal. Colloques Internationaux No.105, Centre National des
Recherches Scientifiques, pp.57-65.
^ Gastuche, M. C. and DeKimpe, C. (1962): La genèse des minéraux
argileux de la famille du kaolin. II. Aspect cristallin. Colloques
Internationaux No.105, Centre National des Recherches Scientifiques,
^ Tamura, T. and Jackson, M. L. (1953): Structural and energy
relationships in the formation of iron and aluminium oxides,
hydroxides, and silicates. Science, vol.117, pp.381-383.
^ Moore, L. R. (1964): The in situ formation and development of some
Clay Minerals Bulletin, vol.5, pp.338-351.
^ Nieuwenburg, C. J. van and Pieters, H. A. J. (1929): Studies on
hydrated aluminium silicates. I. The rehydration of metakaolin and the
synthesis of kaolin. Recueils des Travaux Chimiques de Pays-Bas,
^ Noll, W. (1934): Hydrothermale Synthese des Kaolins. Tschermaks
Mineralogische und Petrographische Mitteilungen, vol.45, pp.175-190.
^ Noll, W. (1936): Über die Bildungsbedingungen von Kaolin,
Montmorillonit, Sericit, Pyrophyllit und Analcim. Tschermaks
Mineralogische und Petrographische Mitteilungen, vol.48, pp.210-247.
^ Norton, F. H. (1939): Hydrothermal formation of clay minerals in the
laboratory. American Mineralogist, vol.24, pp.1-17.
^ Roy, R. and Osborn, E. F. (1954): The system alumina – silica –
water. American Mineralogist, vol.39, pp.853-885.
^ Roy, R. (1962): The preparation and properties of synthetic clay
minerals. Colloques Internationaux No.105, Centre National des
Recherches Scientifiques, pp.83-98.
^ Hawkins, D. B and Roy, R. (1962): Electrolytic synthesis of
kaolinite under hydrothermal conditions. Journal of the American
Ceramic Society, vol.45, pp.507-508.
^ Tomura, S.; Shibasaki, Y.; Mizuta, H. and Kitamura, M. (1985):
Growth conditions and genesis of spherical and platy kaolinite. Clays
Clay Minerals, vol.33, pp.200-206.
^ Satokawa, S.; Osaki, Y.; Samejima, S.; Miyawaki, R.; Tomura, S.;
Shibasaki, Y. and Sugahara, Y. (1994): Effects of the structure of
silica-alumina gel on the hydrothermal synthesis of kaolinite. Clays
Clay Minerals, vol.42, pp.288-297.
^ Huertas, F. J.; Fiore, S.; Huertas, F. and Linares, J. (1999):
Experimental study of the hydrothermal formation of kaolinite.
Chemical Geology, vol.156, pp.171-190.
^ Brindley, G. W. and DeKimpe, C. (1961): Attempted low-temperature
syntheses of kaolin minerals. Nature, vol.190, p.254.
^ DeKimpe, C. R. (1969): Crystallization of kaolinite at low
temperature from an alumina-silicic gel. Clays and
^ Bogatyrev, B. A.; Mateeva, L. A.; Zhukov, V. V. and Magazina, L. O.
(1997): Low-temperature synthesis of kaolinite and halloysite on the
gibbsite – silicic acid solution system. Transactions (Doklady) of
the Russian Academy of Sciences / Earth science sections, vol.353 A,
^ DeKimpe, C. R.; Gastuche, M. C. and Brindley, G. W. (1961): Ionic
coordination in alumino-silicic acids in relation to clay mineral
formation. American Mineralogist, vol.46, pp.1370-1381.
^ Harder, H. (1978): Synthesen von Tonmineralen unter spezieller
Berücksichtigung festländischer Bedingungen. Schriftenreihe für
geologische Wissenschaften (Berlin), vol.11, pp.51-78.
^ Murray, Haydn (18 September 2016). "CORRELATION OF PAPER-COATING
QUALITY WITH DEGREE OF CRYSTAL PERFECTION OF KAOLINITE" (PDF).
Department of Geology, Indiana University, Bloomington, Indiana.
^ Rowe, Aaron (24 April 2008). "Nanoparticles help gauze stop gushing
wounds". Wired.com. Archived from the original on 6 July 2009.
^ "Stokoderm® Protect PURE product leaflet - a Kaolin containing skin
protection cream" (PDF). Retrieved 23 March 2016.
^ Ciullo, Peter A. (1996).
Industrial minerals and their uses: a
handbook and formulary. William Andrew. pp. 41–43.
^ Edison Diamond Disc information
^ Diamond, Jared M. (1999). "Evolutionary biology: Dirty eating for
healthy living". Nature. Nature. 400 (6740): 120–121.
^ "Secrets et rituels des femmes camerounaises." (Secrets and rituals
of women in Cameroon) at Gennybeauté.com (in French) Archived 22 July
2014 at the Wayback Machine.
^ Useful in
Ayurveda based herbal packs for
Acne prone skin.
^ Leiviskä, Tiina; Gehör, Seppo; Eijärvi, Erkki; Sarpola, Arja;
Tanskanen, Juha (10 April 2012). "Characteristics and potential
applications of coarse clay fractions from Puolanka, Finland". Central
European Journal of Engineering. 2 (2): 239–247.
^ Franklin Kamtche. "Balengou : autour des mines." (Balengou:
around the mines) Le Jour. 12 January 2010. (in French) Archived 4
March 2012 at the Wayback Machine.
^ Gerald N. Callahan. "Eating Dirt." Emerging Infectious Diseases. 9.8
^ a b R. Kevin Grigsby "
Clay Eating." New Georgia Encyclopedia. 3
^ Chen, Linda (2014-04-02). "The Old And Mysterious Practice Of Eating
Dirt, Revealed". NPR. Retrieved 2014-04-12.
^ "CDC - NIOSH Pocket Guide to Chemical Hazards - Kaolin".
www.cdc.gov. Retrieved 2015-11-06.
Deer, W.A., Howie, R.A., and Zussman, J. (1992) An introduction to the
rock-forming minerals (2nd ed.). Harlow: Longman
Hurlbut, Cornelius S., Klein, Cornelis (1985) Manual of mineralogy –
after J. D. Dana, 20th ed., Wiley, pp. 428–429,
Breck, D.W. (1984) Zeolite molecular sieves, Robert E., Brieger
Publishing Company: Malabar, FL, pp. 314–315,
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CDC – NIOSH Pocket Guide to Chemical Hazards
Clay mineral group
1. Serpentine and chlorite are sometimes considered clay minerals