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


bowleyite an obsolete term for bityite bowlingite



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bowleyite an obsolete term for bityite
bowlingite an obsolete term for a saponite-rich material from near Bowling, Dumbarton, Scotland

brammallite an aluminum-rich dioctahedral mica that shows interlayer deficiency and limited substitutions of Al in the tetrahedral sites. It is a series name (Rieder et al., 1998) with a generalized composition of Na0.65Al2▫Al0.65Si3.35O10(OH)2. Series names designate that additional research may be warranted.
brandisite an obsolete varietal term for clintonite
bravaisite a poorly defined material, possibly illite and montmorillonite
brindleyite a platy serpentine with an ideal composition of (Ni1.75Al1.0)(Si1.5Al0.5)O5(OH)4. Crystals are generally poorly crystalline mixtures of hexagonal and monoclinic polytypes. Poorly described, Al-rich material similar to a Ni analogue of amesite (referred to as “nimesite”) was redefined as brindleyite. Brindleyite is compositionally similar to berthierine because of the tetrahedral Si/Al ratio and structurally similar owing to the hexagonal and monoclinic polytype intergrowths. Brindleyite has been found in the Marmara bauxite deposit, Greece. Cf., amesite, berthierine, garnierite, nepouite, pecoraite, pimelite, willemseite
brinrobertsite a regularly ordered interstratification of a pyrophyllite-like layer and dioctahedral smectite-like layer in a ratio of 1:1 (Dong et al., 2002) Cf., interstratification
bronzite (Finch) an obsolete varietal term for clintonite
brown mica an obsolete name for astrophyllite
brucite Brucite is a hydroxide mineral with the composition of Mg(OH)2. Also, brucite has been used as a group name for M2+(OH)2 where M = Fe, Mg, Mn, Ni. Brucite is comprised of a plane of Mg cations, with each Mg octahedrally coordinated by edge-sharing OH groups, thus forming an infinite two-dimensional sheet. Brucite primarily occurs as a contact metmorphic mineral in dolomites and Mg-rich limestones from the alteration of periclase, and in serpentinites and chlorite schists.
brunsvigite an obsolete varietal term for manganoan zincian chamosite. See chlorite
buldymite a poorly defined material, possibly biotite and vermiculite or interlayer-deficient biotite
bulgakite see astrophyllite group
buserite a synthetic phase, see birnessite
Calgon® see Part 1 of Glossary
Carborundum® see Part 1 of Glossary
chabazite see zeolite
caesium-biotite an obsolete varietal term for biotite
cairncrossite see reyerite group
calciobiotite an obsolete varietal term for biotite
calciotalc an obsolete varietal term for clintonite
cathkinite an obsolete term for a chocolate-brown saponite-rich material from Cathkin Hills, Scotland
carlosturanite Carlosturanite is a rare antigorite-like mineral that apparently contains vacant tetrahedral sites which interrupt the continuity of the tetrahedral sheet without affecting the continuity of the octahedral sheet (Mellini et al., 1985). The structure is thus similar to a modulated serpentine. To maintain charge balance, OH groups substitute for O atoms. The generalized formula is M21[T12O28(OH)4](OH)30.H2O, where M = Mg, Fe3+, Mn2+, Ti4+, and Cr3+, and T = Si, Al. Alberico (1998) showed that there are problems with the model of Mellini et al. (1985), and suggested the need to reexamine the structure. Important occurrences are related to low grade metamorphic (serpentinite) environments. Cf., antigorite
carrboydite see hydrotalcite group
caryopilite a modulated layer silicate based on the serpentine structure, with an approximate ideal composition of Mn2+3Si2O5(OH)4. Fe, Mg, and Al can substitute for Mn. There is an apparent excess of Si and an apparent deficiency in octahedral composition on the basis of 7 oxygen atoms. Earlier literature sometimes described caryopilite as bementite, but it has been shown that they are separate species. A monoclinic polytype is dominant and small amounts of a trigonal phase are often intergrown. Caryopilite, like greenalite, is an “island” structure where Si-rich tetrahedra of a given layer have apical oxygen atoms coordinate to one octahedral sheet and others to the adjacent sheet (Guggenheim and Eggleton, 1998). The islands are saucer-shaped with some islands inverted, and the islands are domed. Island diameters depend on composition with larger-diameter islands having smaller average octahedral cation sizes (4 tetrahedral-ring diameters in greenalite, 3 rings in caryopilite). Island domains are randomly displaced within layers. “Baumite”, a mixture of several phases, contains a phase, probably Zn,Mg-rich, that is intermediate in domain structure to greenalite and caryopilite. Caryopilite is commonly found in bedded manganese deposits, such as those at the North Chichibu belt in the Shikoku region, SW Japan. Cf., greenalite
caswellite a poorly defined material, possibly mica and manganoan andradite
cat gold an obsolete term for muscovite
cat silver an obsolete term for muscovite
cataspilite a poorly defined material, possibly alteration product with dominant muscovite

catlinite a poorly defined material, possibly muscovite and pyrophyllite
celadonite a dioctahedral member of the true mica group. The end-member formula is KFe3+(Mg, Fe2+)▫Si4O10(OH)2. Typical range in composition is: viR2+/(viR2+ + viR3+) ≥ 0.25, viAl/(viAl + viFe3+) < 0.5, Mg/(Mg + viFe2+) > 0.5 (Rieder et al., 1998).
cerolite equivalent to kerolite, see kerolite
chacaltaite a poorly defined material, possibly an illite pseudomorph after cordierite
chacaltocite an obsolete term for muscovite
chalcedony Chalcedony is a rock term to describe a mixture of a fibrous [110] variety of microcrystalline (length fast) quartz and moganite. Cf., quartzine
chalcodite an obsolete varietal term for stilpnomelane
chalcophanite see birnessite
chamosite the Fe-rich member of the chlorite group with a composition of ideally Fe2+5Al (Si3Al)O10(OH)8. There may be considerable substitutions of Mg, Fe3+, and Al for Fe2+. The common polytype is the IIb form, a one-layer form. Chamosite is an important constituent in oolitic and sedimentary iron formations and may be found as grain coatings in sandstones. See chlorite
chernykhite a dioctahedral member of the brittle mica group. The end-member formula is: BaV2▫Al2Si2O10(OH)2. Typical site substitutions primarily occur in the octahedral site by Al, Fe, and/or Mg.
chert Chert is a rock term to describe an authigenic species of SiO2 which consists of nanoscale intergrowths of quartz and moganite, a metastable SiO2 polymorph (Heaney, 1994). Cf., moganite, quartz
chlorite/smectite (or chlorite-smectite) terminology commonly used to denote the interstratification of chlorite or chlorite-like layers with smectite or smectite-like layers. Alternatively, this interstratification can be described as chlorite/corrensite. It may be abbreviated as C/S or C-S. Because the interstratification is not regular, it is not recognized as a unique phase. Cf., chlorite, corrensite, smectite
chlorite a group name for phyllosilicates with the general formula of (R2+6-y-z R3+yz) (Si4-x R3+x)O10(OH)8 where ▫ represents vacancies, x is the number of tetrahedral R3+ cations, y is the number of octahedral R3+ cations, and z is the number of vacancies. The common structure consists of negatively charged trioctahedral 2:1 layers alternating regularly with positively charged trioctahedral interlayer sheets. Ideal composition of the 2:1 layer is (R2+, R3+)3 (Si4-x R3+x)O10(OH)2 and that of the interlayer is (R2+, R3+)3(OH)6. Bayliss (1975) defined trioctahedral end members based on the dominant cation, e.g., Fe-rich, chamosite; Mg-rich, clinochlore; Mn-rich, pennantite; Ni-rich, nimite; Zn-rich, baileychlore. The trioctahedral chlorites are commonly found in metamorphic rocks and are the diagnostic mineral of the greenschist facies. Chlorite is also a common alteration product. Eggleton and Bailey (1967) combined composition and structure characteristics to define dioctahedral chlorite species. Cookeite is the Li-rich chlorite, whereas sudoite is essentially Li-free. Cookeite and sudoite occur in pegmatite, hydrothermal deposits, and ore deposits. Both have a dioctahedral 2:1 layer and a trioctahedral interlayer (di, trioctahedral chlorite). Donbassite has two dioctahedral sheets (di,dioctahedral chlorite) and is Al-rich. For trioctahedral chlorite, the common polytype is the one-layer, IIb form, although cookeite, commonly forms in the one-layer Ia form (cf., Ia polytype, IIb polytype). See also Part 1 of the Glossary.
chlormagaluminite see hydrotalcite group
chloropal an obsolete term for nontronite
chlorophanerite an obsolete term for glauconite
chlorophœite a poorly defined material, found as infillings in cavities in basic igneous rocks, possibly an altered chlorite
chrombiotite an obsolete varietal term for biotite
chrome mica an obsolete term for chromian muscovite, chromian phengite
chromglimmer an obsolete term for chromian muscovite, chromian phengite
chromochre an obsolete term for chromian muscovite
chromphyllite a dioctahedral member of the true mica group. The end-member formula is KCr2▫AlSi3O10(OH,F)2.
chrysophane an obsolete term for clintonite
chrysotile a member of the serpentine group with textures showing packets of cylinders, scrolls, and tubes, as well as helical or spiral fibers. Chrysotile, ideally Mg3Si2O5(OH)4, crystallizes in monoclinic symmetry (clinochrysotile) with the fiber axis parallel to X and orthorhombic symmetry with the fiber axis along X (orthochrysotile) or Y (parachrysotile). Polytype stacking for clinochrysotile is either 2Mc1 or 1Mc1, where the number of layers (e.g., 1 or 2) precedes M = monoclinic, subscript c = cylindrical, and subscript 1 is used to distinguish the form from another cylindrical polytype that would otherwise have the same symbol. The orthochrysotile polytype is 2Oc1. Cylindrical structures do not have consistent hydrogen bonding between layers that would be observed in an ideal platy structure, and thus do not conform to the standard polytypes. Fiber dimensions are variable with inner diameters near 70-80 Å and outer diameters reported at 220-270, >350, and 490 Å (the latter value involves synthetic samples). Al, Fe2+, and Fe3+ may substitute for Mg, and Fe3+ may substitute for Si; all substitutions are very limited, but greater than in lizardite. The differences between these substitutions in lizardite vs. chrysotile suggest that in natural systems, lizardite and chrysotile are not sensu stricto polymorphs. Chrysotile, or “white asbestos”, is the asbestosform serpentine and is mined in Russia near the Ural Mountains and in Asbestos, Quebec, Canada.
clingmanite an obsolete term for margarite
clinochlore the trioctahedral Mg-rich member of the chlorite group. See chlorite
clinoptilolite see zeolite
clinotobermorite see tobermorite
clintonite a trioctahedral member of the brittle mica group. The end-member formula is: CaMg2Al(Al3Si)O10(OH)2. Typical site substitutions include: Ca > Na,K; Fe2+, Al, Fe3+, Mn for Mg; and Al and Fe3+ for Si or ivAl.
coalingite see hydrotalcite group
colomite an obsolete term for roscoelite
common mica an obsolete term for muscovite
confolensite an obsolete, local term for montmorillonite from Confolens, Charente, France
connarite an obsolete varietal term for willemseite
cookeite a Li-bearing member of the chlorite group, with an ideal composition of (Li,Al4)(Si3Al)O10(OH)8. The octahedral sheet of the 2:1 layer is dioctahedral and the interlayer is trioctahedral, therefore this is a di,trioctahedral chlorite. The common polytype is based on the Ia structure. Cf., chlorite
coombsite see zussmanite
coronadite see hollandite
corrensite a regular interstratification of trioctahedral chlorite-like layers with either trioctahedral smectite-like or trioctahedral vermiculite-like layers, the former being “low-charge corrensite” and the latter “high-charge corrensite”. The ratio of chlorite-like layers to smectite-like or vermiculite-like layers is 1:1 (Guggenheim et al., 2006). Corrensite occurrences are from low temperature environments, such as evaporites, saline deposits, sedimentary rocks, weathering zones, hydrothermal systems, burial diagenesis, low grade metamorphic regimes, and some contact metamorphic zones. Beaufort et al. (1997) discussed corrensite possibly as a regular mixed-layer structure involving a continuous series from smectite (or vermiculite) to chlorite or alternatively, as a single phase with a regular alteration of chlorite and smectite (or vermiculite) layers, with a stability field. If the latter, mixtures that deviate from 1:1 ratios of interstratified layers would require physical mixtures of appropriate layers of corrensite and chlorite.
corundellite an obsolete term for margarite
corundophilite an obsolete term for low-Si (and variable amounts of Fe2O3) chlorite
cossaite an obsolete varietal term for paragonite
cristobalite Beta-cristobalite, a high temperature (above 1470 oC, but below liquid at 1727 oC at 1 bar) polymorph of SiO2, has an ideal basic structure that is polytypic with tridymite. Like tridymite, beta cristobalite has sheets of hexagonal tetrahedral rings with alternate tetrahedra around a ring with apices pointing in opposite directions from adjacent tetrahedra. These sheets have an ABCABC... stacking sequence, which creates an offset such that no channels form as they do in tridymite. Cristobalite is found in volcanic rocks, primarily in a fine groundmass, but also as a lining of cavities and as a devitrification of volcanic glasses. Cf., opal, tridymite, quartz
cronstedtite Cronstedtite is the Fe-rich serpentine of composition (R2+3-xFe3+x)(Si2-xFe3+x) O5(OH)4. Divalent cations (R2+) may include Fe, Mg, Mn, and possibly Ca. It is assumed that the value of x in the formula is equal (and near 0.5 to 1.0) for both the tetrahedral and the octahedral sites. Cronstedtite has a large number of polytypes, with the 1T (space group P31m) most common. The lateral dimensions of the iron-rich tetrahedral sheet are large, but the lateral dimensions of the octahedral sheet are large also, and thus tetrahedral rotation ranges only up to ~8 o. Because most (possibly all) of the iron is ferric, the tetrahedral-octahedral misfit is limited. Fe3+ and Si segregate to different T sites in the 2H2 polytype, but not in the 1T, 3T, 2H1, and 6R2 polytypes. Amesite-2H2 also shows tetrahedral ordering, but between Al and Si. Cronstedtite forms in low-temperature hydrothermal veins with other iron rich minerals, such as siderite, and in low-temperature metamorphosed iron formations. It is also known to occur in carbonaceous chondrites. The Mn analogue of cronstedtite is guidottiite. Cf., amesite, greenalite, guidottiite
cryophyllite an obsolete varietal term for zinnwaldite, ferroan trilithionite, and ferroan polylithionite
cryptomelane see hollandite
culsageeite an obsolete name for altered material, probably vermiculite
cymatolite a poorly defined material, possibly muscovite and albite
damourite an obsolete term for muscovite
daphnite an obsolete term for a low-Si chlorite
delessite an obsolete term for a chlorite material, rich in ferric iron, probably a Mg-rich chamosite
de saulesite a discredited term for pimelite
desautelsite see hydrotalcite group
devitoite see astrophyllite group
deweylite an obsolete term for a mixture of poorly crystalline phyllosilicates (1:1 and 2:1 types). When red, “deweylite” was called “eisengymnite”, and when found at Bare Hills, Maryland, USA, “deweylite” was called “gymnite”.
diabantite a discredited term for a Si- and Fe-rich (clinochlore) chlorite
diaspore a polymorph of hydrous aluminum oxide, alpha-AlO(OH), and isostructural with goethite, alpha-FeO(OH). The structure is comprised of double chains of edge-sharing octahedra of AlO3(OH)3 along the c axis, and the chains are offset along the b axis. Diaspore occurs with corundum, often in chlorite schists and in dolomite, and as a major constituent as fine-grained matrix in bauxite.

dickite a member of the kaolin group, which consists of the dioctahedral and aluminous rich 1:1 phyllosilicates. Dickite has a chemical composition of Al2Si2O5(OH)4. Dickite is distinguished from the other polymorphs, kaolinite and nacrite, by the vacant octahedral site regularly alternating from layer to layer across “B” and “C” sites. Thus, the polytype is a two layer form with monoclinic symmetry, Cc. The “B” and “C” sites would be related by a mirror plane if both sites were occupied identically within the same layer, whereas the “A” site resides on the mirror plane (Bish and Johnston, 1993). Dickite has a widespread occurrence and often is believed to be transformed from kaolinite (and therefore dickite is the more stable phase) by higher temperature (various temperatures have been suggested depending on origin, e.g., ~120 oC, 290 - 300 oC, 80 - 160 oC), but dissolution-precipitation of kaolinite to dickite has been suggested also, as well as direct precipitation. Dickite has been described from hydrothermal and diagenetic environments. Examples of hydrothermal dickite include those of Japan and Nayarit, Mexico. Cf., halloysite, kaolin, kaolinite, nacrite
didrimite an obsolete term for muscovite
didymite an obsolete term for muscovite
diphanite an obsolete term for margarite
disterrite an obsolete varietal term for clintonite
donbassite a member of the chlorite group, with an ideal formula of (Al 4+x/3Si4-xAlx)O10(OH)8, where x represents excess Al. Both octahedral sheets are dioctahedral, therefore this is a di,dioctahedral chlorite. Cf., chlorite
dozyite a regular interstratification of trioctahedral serpentine with trioctahedral (i.e., tri,trioctahedral) chlorite. The ratio of chlorite layers (i.e., one 2:1 layer and one interlayer) to serpentine (i.e., one 1:1 layer) is 1:1. The name applies to any composition of interstratified trioctahedral serpentine or trioctahedral chlorite regardless of the structure type (i.e., stacking) of the chlorite. Variations in chemical composition other than Mg and Al may be noted by descriptive adjectival modifiers (Bailey et al., 1995).
dudleyite a poorly defined material, possibly smectite or vermiculite
dysintribite an obsolete term for muscovite
eastonite a trioctahedral member of the true mica group. The end-member formula is KMg2Al(Al2Si2)O10(OH)2. The original eastonite occurrence from Easton, Pennsylvania, USA, was shown to be a mixture of phlogopite and lizardite-1T with some “antigorite-like offsets”.
eggletonite see ganophyllite
eisengymnite see “deweylite”
ekmanite a 2:1 modulated phyllosilicate having an ideal chemical composition of KM20Si32O76(OH)17, where M = Fe2+, Mg, Mn2+. Analyses show that Ca and Na substitutes for K, Fe3+ substitutes for M, and Al substitutes for Si. Ekmanite has a highly disordered layer-stacking. The proposed model (Ferrow et al, 1999), based on TEM analysis, has strips of tetrahedra attached to the continuous octahedral sheet, with the strips along the a axis. The basic layer is 2:1 with inverted tetrahedra linking across the interlayer through apical oxygen atoms, with three of eight tetrahedra linking the 2:1 layers and inverted relative to adjacent octahedral sheets, similar to bannisterite. All tetrahedral rings are 6-fold, unlike bannisterite. Ekmanite is known from the magnetite ore body and skarns at Brunnsjögruvan, Sweden, in rocks metamorphosed to greenschist facies.
elhuyarite an obsolete term for allophane associated with lignite from Friesdorf, Germany
emerylite an obsolete term for margarite
endellite a redundant term for halloysite and its use should be discontinued
ephesite a trioctahedral member of the true mica group. The end-member formula is NaLiAl2(Al2Si2)O10(OH)2.
epichlorite a poorly defined material, possibly an altered chlorite
epileucite a poorly defined material, possibly a muscovite and K-rich feldspar pseudomorph after cordierite
episericite a poorly defined material, possibly illite
erionite see zeolite
errite an obsolete (light green) variety of parsettensite
eukamptite a poorly defined material, possibly altered biotite
euchlorite an obsolete term for biotite
euphyllite a poorly defined material, possibly paragonite and muscovite or paragonite
euralite a poorly defined material, possibly an altered chlorite found as infillings in cavities in basic igneous rocks
falcondoite a member of the palygorskite-sepiolite group with a composition of approximately (Ni8-y-z R3+yz) (Si12-x R3+x) O30 (OH)4 (OH2)4 . R2+(x-y+2z)2 (H2O)8, where R is a cation, ☐ are vacancies, and x, y, and z are compositional parameters. See palygorskite-sepiolite group
faratsihite a poorly defined material, probably a mixture of kaolin and nontronite
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