The Clay Minerals Society Glossary of Clay Science, 2018 version Part Clay-Related Materials (Excluding exchanged phases) achlusite



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The Clay Minerals Society Glossary of Clay Science, 2018 version

Part 2. Clay-Related Materials (Excluding exchanged phases)
achlusite a poorly defined material, possibly sodium mica
adamsite an obsolete term for muscovite
agalite an obsolete, local term for a fibrous talc from New York State, USA; or for pyrophyllite from China (also obsolete)
agalmatolite an obsolete term for pyrophyllite or a mixture with dominant pyrophyllite
aliettite a regularly ordered interstratification of a talc-like layer and trioctahedral smectite-like layer in a ratio of 1:1 (Veniale and van der Marel, 1969; Bailey, 1981). Cf., interstratification

allevardite obsolete name replaced by rectorite, see rectorite
allophane a semiordered hydrous aluminosilicate, Al2O3(SiO2)1.3-2.02.5-3.0(H2O), that is closely related to imogolite because both seem to be incipient 1:1 minerals structurally and chemically, although it has been suggested that allophane may be an incipient montmorillonite. The ratio of SiO2 to Al2O3 is usually 1.3 to 2.0 for allophane, but has been reported as low as 0.83, a greater variation than in imogolite. Allophane shows curved walls with a more spherical morphology (30 - 50 Å spherical diameters) than imogolite, which is tube-like. Allophane is common in soils derived from volcanic ash, but may be present in soils derived from basic igneous rocks in tropical climates or in podzol soils derived from more acidic rocks. Allophane may precipitate in hot springs rich in silicic acid and aluminum. Allophane is white or colorless when moist, but earthy when dried. Syn., disordered allophane, Cf., imogolite

aluminoceladonite a dioctahedral member of the true mica group. The end-member formula is KAl(Mg,Fe3+) ▫Si4O10(OH)2, where ▫ = vacancy. Typical range in composition is: viR2+/(viR2+ + viR3+) ≥ 0.25, viAl/(viAl + viFe3+) = 0.5 - 1.0, Mg/(Mg + viFe2+) > 0.5 (Rieder et al., 1998).
alurgite an obsolete varietal term for manganoan muscovite and manganoan illite
alushtite known only in the Russian literature and not an official mineral name; the accepted name is tosudite
amesite a (trioctahedral) platy serpentine mineral of ideal composition of Mg2Al(Si,Al)O5(OH)4. Fe2+, Mn, Cr, Ni, and vacancies may substitute for Mg and viAl in natural samples. Natural occurrences are rare and have been noted from the Saranovskoye chrome deposit, North Urals Mountains, Russia; Chester, Massachusetts, USA; Mount Sobotka, Poland; Postmasburg, South Africa; Lake Asbestos Mine, Black Lake, Quebec, Canada; and Antarctica. The Quebec occurrence involves a rodingitized granite within a serpentinized peridotite. Stacking disorder is common but, where regular layer stacking occurs, it is most often based on a distorted 2H2 layer sequence (space group C1). Cf., kellyite, zinalsite.


ammochrysos an obsolete term for muscovite
ammonium hydromica an obsolete term for tobelite
ammonium muscovite an obsolete term for tobelite
amphilogite an obsolete term for muscovite
anandite a trioctahedral member of the brittle mica group. The end-member formula is: BaFe2+3(Fe3+Si3)O10S,OH. Typical site substitutions include: Ba > K,Na; Mg, Fe3+, Mn, Al for Fe2+; and S > OH,Cl,F. Anandite occurs in a banded magnetite-barite-sulfide ore within meta-sedimentary granulite facies at the Wilagedera iron ore prospect, North Western Province, Sri Lanka, and it has been reported at Rush Creek and Big Creek, Fresno County, California, USA, and Sterling Hill, New Jersey, USA, although the latter occurrences are in doubt because of the lack of structural S, a requirement for the species (Bujnowski et al., 2009). Anandite occurs as 2O and 2M1 polytypes, and a 2M polytype based on a 1M stacking sub-structure.
anauxite a discredited term for kaolinite
ankangite a discredited manganese oxide mineral better described by the H2O-free variety of mannardite, see hollandite

annite a trioctahedral member of the true mica group. The end-member formula is KFe2+3 AlSi3O10(OH)2.
anomite an obsolete term for biotite
antigorite a platy serpentine with lath-like characteristics. Diffraction studies have shown an atomic superstructure arrangement approximately along the [100] direction. The origin of the superstructure is the tetrahedral repeat unit involving tetrahedral reversals in + or - directions along the c axis to form a wave-like structure. Antigorite structures have been shown by single-crystal X-ray diffraction to have, for example, a wave structure involving a tetrahedral repeat of 17 and one with two waves of tetrahedral repeats of 16, although other wavelengths are possible (from 12 to 21). For the 17 tetrahedral repeat, there is a half-wave width of 8 tetrahedra and 9 tetrahedra (Capitani and Mellini, 2004). At one reversal in each unit cell, there are 4- and 8-fold tetrahedral rings, but only 6-fold tetrahedral rings at the other reversal. Between reversal points, the tetrahedral rings are 6-fold. The generalized formula is ideally: M3m-3T2mO5m(OH)4m-6 where M = six-coordinated cations, T = Si, Al, and m = tetrahedral repeat along the superstructure direction, usually the [100]. M is predominantly Mg, but may have Fe (mostly Fe2+), Ni, Cr, and Al. Because each superstructure type affects the composition, these forms are not sensu stricto polymorphs of each other or between lizardite and chrysotile. Each half wave has a curvature, either concave up (+ c axis) or concave down (- c axis). The interlayer in an ideal serpentine is occupied by hydrogen bonds, which link adjacent 1:1 layers. In antigorite, linkage across this region is by tetrahedra, and polytypism cannot describe the stacking structure. For m = 17, the space group symmetry is Pm, for m = 16, the space group is C2/m. Antigorite is commonly found in igneous or metamorphic serpentinites. Serpentine rock is mostly comprised of antigorite and lizardite. Cf., carlosturanite, chrysotile, lizardite

antrophyllite a poorly defined material, possibly a mica
aphrosiderite an obsolete term for chlorite filling cavities in igneous rocks, possibly chamosite
armbrusterite a modulated 2:1 layer silicate with a continuous octahedral sheet containing Mn and Na and tetrahedral sheets having 5-, 6-, 7-, and 8-fold tetrahedral rings (Yakovenchuk et al., 2007). One symmetry-unique Si tetrahedron is inverted relative to the others in the sheet and this tetrahedron links two adjacent tetrahedral sheets. The other tetrahedra link to the octahedral sheets. The ideal chemical composition is K5Na6Mn3+Mn2+14(Si9O22)4(OH)10 . 4H2O. Armbrusterite is found in the Khibiny alkaline massif, Kola Peninsula, Russia. Cf., bementite, parsettensite, pyrosmalite, innsbruckite, varennesite
asbestos see Part 1 of Glossary
aspidolite a trioctahedral member of the true mica group. The end-member formula is NaMg3AlSi3O10(OH)2.
astrolite an obsolete term for muscovite
astrophyllite see astrophyllite group
astrophyllite group The general formula (as given by Sokolova and Hawthorne, 2016) for the astrophyllite group minerals is A2pBrC7D2(T4O12)2IXOD2XOA4XPDnWA2 where C represents cations at the M(1-4) sites in the O sheet and are commonly Fe2+, Mn, Na, Mg, Zn, Fe3+, Ca, Zr, Li; D represents cations in the H sheet and are either in 6 or 5 coordination and are Ti, Nb, Zr, Sn4+, 5Fe3+, Mg, Al; T = Si, Al; A2pBrWA2 (I block) with p =1, 2; r = 1, 2; A = K, Rb, Cs, Ba, H2O, Li, Pb2+, Na, ▫ where ▫ = vacancy; B = Na, Ca, Ba, H2O, ▫; Xo refers to anions in the O sheet not bonded to T sites, XOD = oxygen anions in common at the 3M and D vertices; XOA = OH, F anions at the common vertices of 3M polyhedra; XPD = F, O, OH, H2O, ▫, apical anions of D cations at the edges of the HOH block; WA = H2O, ▫; and for XPDn, n = 0. 1, 2.

The astrophyllite group minerals form 2:1 phyllosilicate-type structures with portions of the structure described as HOH (analogous to TOT in 2:1 phyllosilicates) with T4O12 ribbons comprising the H (heterogeneous, hetero- meaning “extra”) sheet. Alternating with HOH blocks are intermediate (I) blocks along the c axis. Sokolova and Hawthorne (2016) described the astrophyllite group as a “supergroup” with three divisions (groups): the astrophyllite group, the kupletskite group and the devitoite group. HOH blocks may link directly (as in astrophyllite group, with Fe2+ dominant) or do not link (as in devitoite group) or direct linkage with Mn2+ dominant (as in kupletskite group). The linkages involve “bridges” of D-XpD-D. These titanosilicates have similar a axial lengths to phyllosilicates (both near 5.4 Å) and d(001) values (~10.9 Å, although somewhat variable vs 10.0 Å in 2:1 phyllosilicates). The supergroup divisions are:


Astrophyllite Group, Fe2+ dominant, direct HOH linkage

astrophyllite K2NaFe2+7Ti2(Si4O12)2O2(OH)4F

niobophyllite K2NaFe2+7(Nb,Ti)(Si4O12)2O2(OH)4(F,O)
zircophyllite K2NaFe2+7Zr2(Si4O12)2O2(OH)4F

bulgakite Li2(Ca,Na)Fe2+7Ti2(Si4O12)2O2(OH)4(F,O)(H2O)2

nalivkinite Li2NaFe2+7Ti2(Si4O12)2O2(OH)4F(H2O)2

tarbagataite (K ▫)CaFe2+7Ti2(Si4O12)2O2(OH)5


Kupletskite Group, Mn2+ dominant, direct HOH linkage

kupletskite-1A K2NaMn7Ti2(Si4O12)2O2(OH)4F

kupletskite-2M K2NaMn7Ti2(Si4O12)2O2(OH)4F

kupletskite-(Cs) Cs2NaMn7Ti2(Si4O12)2O2(OH)4F

niobokupletskite K2NaMn7(Nb,Ti)(Si4O12)2O2(OH)4(O,F)
Devitoite group

devitoite Ba6Fe2+7Fe3+2(Si4O12)2(PO4)2(CO3)O2(OH)4

sveinbergeite (H2O)2[Ca(H2O)](Fe2+6Fe3+)Ti2(Si4O12)2O2(OH)4(OH,H2O)

lobanovite K2Na(Fe2+4Mg2Na)Ti2(Si4O12)2O2(OH)4


HOH blocks are found in other (heterophyllosilicate) titanosilicates, and these minerals have been described by Ferraris and co-workers (e.g., for a partial summary, see Ferraris, 1997). These include nafertisite [Na,K, ▫)4(Fe2+,Fe3+, ▫)10(Ti2O3Si12O34)(O,OH)6], bafertisite [(Ba2(Fe,Mn)4(Ti2O4Si4O14)(O,OH)2], perraultite [KBaNa2(Mn,Fe2+)8(Ti,Nb)4Si8O32(OH,F,H2O)7], lamprophyllite Na2(Sr,Ti,Na,Fe)4(Ti2O2Si4O14)(O,F)2, seidozerite (Na2(Na,Mn,Ti)4 [(Na,Ti,Zr)2 O2Si4O14]F2), and many others. The titanosilicates are found in hyperagpaitic (highly peralkaline nepheline syenites) rocks.
attapulgite 1) refers to the mineral, palygorskite, and should not be used in the mineralogic or geologic literature. See Guggenheim et al. (2006) and references therein. 2) Attapulgite is a common, globally used industrial term synonymous with palygorskite; especially, where mined and processed in the Florida-Georgia region of the United States or other commercial deposits around the world (e.g., China, Spain, Senegal, India, Australia, Greece, Turkey and Ukraine).
avalite a poorly defined material, possibly chromian illite or a mineral mixture
baddeckite a poorly defined material, possibly muscovite and hematite
bafertisite see astrophyllite group
baileychlore the trioctahedral Zn-rich member of the chlorite group. Also, see Part 1. General terms: group names, chlorite
balestraite a member of the mica group characterized by octahedral vanadium and lithium and free from Al and OH, with a chemical composition of ideally KLi2VSi4O12. Balestraite occurs in subgroup C2 symmetry because of octahedral ordering and as a 1M polytype. Balestraite occurs in Mn-rich beds within metacherts of an ophiolite sequence and was located between carbonate-rich and hematite bands at the Cerchiara mine, Eastern Liguria, Italy.
baltimorite see picrolite
bannisterite a modulated, trioctahedral, mica-like layer silicate with cross-linked inverted tetrahedra with an idealized formula of Ca0.5K0.5M10(Si14.5Al1.5)O38(OH)8 . nH2O where M is medium-size divalent cations, such as Fe, Mn, Zn, Mg, and n = 2 - 6 (Heaney et al., 1992). The tetrahedral sheet consists of 5-, 6-, and 7-fold rings. Important localities for bannisterite include Franklin, New Jersey (USA), Broken Hill, Australia, and Nyberget, Sweden; localities with abundant Mn silicates.
barbertonite see hydrotalcite group
bardolite a poorly defined material, possibly interstratified biotite and vermiculite
basonite a poorly defined material, possibly interstratified biotite and vermiculite
bastite an obsolete term describing a pseudomorph comprised of serpentine altered from a Mg-rich pyroxene
barium phlogopite an obsolete varietal term for phlogopite
barytbiotite an obsolete varietal term for phlogopite
bastonite a poorly defined material, possibly interstratified biotite and vermiculite
baumite discredited name because it is a mixture of several phases; see caryopilite
bauxite see Part 1 of Glossary
bavalite an obsolete term for oolitic chlorite, possibly chamosite
bayerite a polymorph of Al(OH)3 that occurs rarely in nature. The gibbsite Al(OH)3 octahedral layer is similar to the dioctahedral layer in bayerite, but the stacking of the layers differs. Small distortions in the bayerite octahedra produce an overall two-layer structure. A notable occurrence for bayerite is in sedimentary rocks from Hartrurim, Israel, where bayerite is in association with calcite, gypsum, portlandite, and ettringite. Cf., gibbsite, nordstrandite
beidellite a dioctahedral member of the smectite group. An important characteristic of this member is that isomorphous substitution occurs primarily in the tetrahedral sites to produce the net negative charge on the 2:1 layer (Güven, 1988). An idealized formula for beidellite is R+0.33Al2(Si3.67Al0.33)O10(OH)2.nH2O, where R is an exchangeable cation, in this case univalent, but other valences are possible. The iron (Fe3+) analogue is known as nontronite and intermediate compositions are known. Beidellite is found abundantly as weathering products of volcanic ash, in association with hydrothermal environments, and as diagenetic products. An especially pure end-member beidellite comes from the Black Jack Mine, Idaho, USA. Cf., smectite.
bementite a modulated 1:1 layer silicate with octahedral sheets interlayered by a continuous tetrahedral sheet with double 6-fold tetrahedral rings (Heinrich et al., 1994). The 6-fold rings are interconnected and have tetrahedra pointing up and down, and adjacent octahedral sheets are connected with 5- and 7-fold tetrahedral rings. The ideal chemical composition is M7Si6O15(OH)8, where M are medium size cations, such as Mn, Fe, Mg, Zn. Small amounts of Al are known to enter the tetrahedral site for Si. Important localities include Franklin, New Jersey, USA in a metamorphosed, zinc stratiform ore body, and the Olympic peninsula, Washington, USA. Cf., armbrusterite, parsettensite, pyrosmalite, innsbruckite, varennesite
bentonite see Part 1 of Glossary
bergseife see “bole”, halloysite
berthierine a member of the serpentine group with an ideal composition of approximately (Fe2+, Mn2+, Mg)3-x (Fe3+, Al)x (Si2-xAlx)O5(OH)4. Berthierine is commonly found in unmetamorphosed sedimentary iron formations. Berthierine occurs more commonly as either an apparent trigonal (possibly 1T) or less commonly as an apparent monoclinic (possibly 1M) polytype, and both polytypes are generally intergrown. Berthierine is often confused in the older literature with chamosite, a member of the chlorite group, but not to be confused with berthierite, a sulfide mineral. Cf., brindleyite, chamosite
bildstein an obsolete term for pyrophyllite or a mixture with dominant pyrophyllite
biotite defined by Rieder et al. (1998) as a trioctahedral mica between, or close to, the annite-phlogopite (i.e., ferrous iron and magnesium substitutions) and siderophyllite-eastonite (i.e., Al rich) joins. The term grandfathers the use of “biotite” in the field, when a chemical analysis is unavailable to describe a dark mica, presumably without Li.
birnessite a layered manganese oxide mineral (phyllomanganate) similar in structure to chalcophanite. The formula of a synthetic sample used in a structure determination (Post and Veblen, 1990) is Mg0.29Mn4+1.42Mn3+0.58O4 . 1.7H2O, assuming no Mn vacancies and an analysis total of 100%. Chalcophanite has a sheet of edge sharing Mn-O octahedra where one in seven octahedra is vacant. Zn cations are located above and below the vacant sites, also in octahedral coordination, with oxygen atoms from the octahedral sheet and from a plane of H2O molecules between the Mn-O sheets. Interlayer cations in birnessite, Mg, Na, K, Ca, etc., may occupy the Zn site and/or H2O sites (as found in chalcophanite). However, distributions of the interlayer cation and H2O sites in birnessite may also differ for various compositions (e.g., Na- vs Mg-rich birnessite), and the occupancy of the interlayer cation/H2O sites is believed to produce observed superstructures. Cation exchange and redox reactions can occur in birnessite. Ranceite is the (interlayer cation) Ca end member of birnessite and takanelite has Mn2+ as the interlayer cation. “Buserite” is a hydrated form of birnessite with a 10-Å spacing instead of the 7-Å value of birnessite. “Buserite” has not been found in nature and is not a mineral, but is a common phase during synthesis of birnessite. Birnessite is a major Mn-rich phase in many soils, in desert varnish, in ocean manganese nodules, and as an alteration product in Mn-rich ore deposits. Australian soils containing birnessite may be related to neutral to slightly alkaline conditions, but this result is not universal and the presence of birnessite may instead be related to a paucity of Ca and Mg of these soils.
biaxial mica an obsolete term for muscovite
bityite A trioctahedral member of the brittle mica group. The end-member formula is: CaLiAl2(BeAlSi2)O10(OH)2. Compositional range restriction includes viLi > vi▫ (i.e., viLi < vi▫ defined as margarite). Cf., margarite
bixbyite Bixbyite, alpha-(Mn3+,Fe3+)2O3, is structurally comprised of edge sharing and corner sharing (Mn,Fe)O6 octahedra. Bixbyite has been reported from non-metamorphosed sediments where it had transformed from todorokite-birnessite, and from hydrothermal and low grade metamorphic deposits.
boehmite Boehmite, or gamma-AlO(OH), is a hydrous aluminum oxide comprised of corrugated sheets of double edge-sharing octahedra of Al–O,OH. Boehmite is isostructural with lepidocrocite, the Fe analogue. Bauxite is a mixture of diaspore, gibbsite, and boehmite, and any one of the three may dominate. Syn., böhmite
böhmite see boehmite
bole an obsolete term for a greasy clay with iron oxide impurities that produce a red, yellow and/or brown color and with about 24% water, possibly primarily halloysite. Syn. “bergseife” for “mountain soap”, also obsolete
borocookeite a boron-rich member of chlorite with an ideal chemical composition of Li1+3xAl4-x (BSi3)O10(OH,F)8 where x = 0.0 to 0.33 atoms per formula unit (Zagorsky et al., 2003). Borocookeite occurs as the Ia polytype. Borocookeite has been found in miarolitic cavities at temperatures greater than 240-265 oC in pegmatite deposits, such as in the Krasny Chikoy district, Chita region, Russia. Cf., manandonite, boromuscovite
boromuscovite a dioctahedral member of the true mica group. The end-member formula is KAl2▫BSi3O10(OH)2. Cf., borocookeite, manandonite
bowenite a transparent, yellow green variety of massive serpentine (antigorite?), used as an alternative for jade. Bowenite is not a mineral name and should not be used in the scientific literature. Syn. tangiwaite or tangawaite (from New Zealand)

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