Clays and Clay Minerals, Vol. 45, No. 2, 298 300, 1997.
REPORT OF THE ASSOCIATION INTERNATIONALE POUR L't~TUDE DES
ARGILES (AIPEA) NOMENCLATURE COMMITTEE FOR 1996
STEPHEN GUGGENHE1M, Chairman, 1 ANDREA ALIETTI,2 VICTOR A. DRITS, 3 MILTON L. L. FORMOSO,4 EMILIO
GALAN,5 HEINRICH M. KOSTER,6 HI~LI~NEPAQUET,7 TAKASHI WATANABE,8 and ex officio m e m b e r s DEREK
C. BAIN (Editor, Clay Minerals) 9 AND WAYNE H. HUDNALL (Editor, Clays and Clay Minerals) 1~
1Department of Geological Sciences, University of Illinois at Chicago, 845 W. Taylor St., Chicago, Illinois 60607
2Institute di Mineralogia e Petrografia, Universita di Modena, Via S. Eufemia 19, 4110 Modena, Italy
3Geological Institute of the Russian Academy of Science, Pyzhevsky Street 7, 109017 Moscow, Russia
49,500, Ave. Bento Gongalves, Campus do Vale, Instit. of Geosciences, University Federal do Rio Grande do Sul, Porto
Alegre, RS, Brazil CEP-91540-000
5Departamento de Cristallografia y Mineralogia, Facultad de Quimica, Apartado 553 Universidad, Sevilla, Spain
6Karl-B6hm-Strasse 191, D-85598 Baldham, Germany
7Centre de Sedimentologie et de Gdochimie de la Surface, Centre National de la Recherche Scientifique, 1 rue Blessig,
67084 Strasbourg Cedex, France
8Joetsu University of Education, Joetsu Niigata 943, Japan
9Macauley Land Use Research Institute, Craigiebuckler, Aberdeen AB9 2QJ, Scotland, Great Britain
~~
Department, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803
Key Words--Commercial Mineral Names, Dickite, Kaolin, Kaolinite, Nacrite, Nomenclature, Polymorphism, Polytypism, Synthetic Mineral Names.
INTRODUCTION
The most recent report of the A I P E A Nomenclature
Committee involved the definition and use of the terms
" c l a y " and "clay mineral"; see Guggenheim and
Martin (1995, 1996). Additional items acted upon by
this committee are reported here.
POLYMORPHISM, POLYTYPISM A N D T H E
KAOLIN MINERALS
Background
" P o l y m o r p h i s m " is the ability of a given element
or compound to crystallize in more than 1 form, with
each form having a distinct crystal structure. "Polytypism" is defined as the existence of an element or
compound in 2 or more layer-like crystal structures
that differ in layer-stacking sequences. The layers need
not be crystallographically identical, but they should
be similar. In part, polytypism differs from polymorphism in permitting small differences in chemical
composition between structures, not to exceed 0.25 atoms per formula unit of any constituent element (see
Bailey 1977, 1980 for additional comments).
In general, polytypes should not receive individual
names. Instead, a set of related polytypes should be
designated by a single name followed by a structural
symbol suffix that defines the layer-stacking differences. Polytype mineral names already in existence
that have international acceptance and serve a useful
function need not be discarded. Decision on the reten-
tion of individual names is the responsibility of the
International Mineralogical Association (IMA) Commission on New Minerals and Mineral Names (Bailey
1977, 1980).
Kaolinite, nacrite and dickite have 1:1 layers with
close similarities in structure. They are polytypes.
Most properly, they should be designated by a single
name followed by a structural symbol suffix that defines the layer stacking sequence. In accord with t h e
above procedures, the Comit6 Internationale Pour
L'6tude des Argiles (CIPEA) Nomenclature Committee (succeeded by the A I P E A Nomenclature Committee) agreed unanimously in 1963 and reconfirmed in
1967 (Brindley 1967) that kaolinite, nacrite and dickite
should be renamed as a single mineral, with symbols
expressing the stacking sequence of kaolinite layers.
In 1971, the Clay Minerals Society (CMS) Nomenclature Committee (Bailey et al. 1971) acknowledged
these changes in its report, but the report left open the
question of the exact nature of the stacking-sequence
symbols pending further study.
Recommendation
The present A I P E A Nomenclature Committee recommends that the names "kaolinite", "nacrite" and
"d i ck i t e" be retained as mineral names, in contrast to
previous committee actions. This action is simply a
recognition that, after nearly 35 years, it is apparent
that the earlier recommendations are not being followed and that the present names are well established
298
Vol. 45, No. 2, 1997
AIPEA Nomenclature Committee Report
Table 1. Recommended use of kaolin and kaolinite in the
classification~ of 1:1 layer silicates.
Layer
type
Group
1: 1
kaolin-serpentine
kaolin
1:1
kaolin-serpentine
serpentine
Subgroup:)
Speciesw
kaolinite, dickite,
nacrite
lizardite, amesite,
berthierine
t Refer to Martin et al. (1991) for a complete classification
scheme.
~: Octahedral character ("dioctahedral" or "trioctahedral")
may be used also.
w Only a few examples are given.
299
olin S y m p o s i u m (1974) as the f o l l o w i n g : " K a o l i n is a
r o c k c h a r a c t e r i z e d b y a useful c o n t e n t o f k a o l i n [sic]
m i n e r a l s . " T h e e c o n o m i c - m i n e r a l o g y aspects w e r e
e l a b o r a t e d b y P a t t e r s o n a n d M u r r a y (1975): " K a o l i n
is a clay c o n s i s t i n g o f s u b s t a n t i a l l y p u r e kaolinite, or
r e l a t e d clay m i n e r a l s , that is n a t u r a l l y or c a n b e ben e f i c i a t e d to b e w h i t e or n e a r l y white, will fire w h i t e
or n e a r l y w h i t e a n d is a m e n a b l e to b e n e f i c i a t i o n b y
k n o w n m e t h o d s to m a k e it suitable for u s e in w h i t e
ware, paper, rubber, p a i n t a n d s i m i l a r u s e s . " In r e c e n t
years, h o w e v e r , the t e r m " k a o l i n " h a s b e e n used int e r c h a n g e a b l y w i t h " k a o l i n i t e " group.
Recommendation
in the literature. F i n a l d e t e r m i n a t i o n o f this m a t t e r resides w i t h i n the I M A C o m m i s s i o n .
G R O U P A N D S U B G R O U P N A M E S F O R 1:1
PHYLLOSILICATES
Background
In 1980, the A I P E A N o m e n c l a t u r e C o m m i t t e e (Bailey 1980) r e c o m m e n d e d a classification s c h e m e o f
p h y l l o s i l i c a t e s in w h i c h 1:1 a n d 2:1 layer types are
d i v i d e d into g r o u p s (for e x a m p l e , k a o l i n i t e - s e r p e n tine) o n the b a s i s o f c h a r g e p e r f o r m u l a unit. S u b g r o u p s (for e x a m p l e , kaolinite, s e r p e n t i n e ) are b a s e d
o n d i o c t a h e d r a l a n d t r i o c t a h e d r a l characteristics. E a c h
s u b g r o u p is f u r t h e r d i v i d e d into m i n e r a l species (for
e x a m p l e , kaolinite, nacrite, dickite, etc. for kaolinite;
lizardite, berthierine, amesite, etc. for serpentine). T h e
classification s c h e m e is not o n l y b a s e d o n details o f
structure, b u t also it c o r r e s p o n d s to a s u c c e s s i o n o f
stages o f r e f i n e m e n t in identification. It was n o t e d that
several " d u a l " n a m e s exist for w h i c h the group, subg r o u p or species n a m e s w e r e identical, as is the c a s e
for kaolinite. T h e C o m m i t t e e r e c o g n i z e d the p o t e n t i a l
for c o n f u s i o n a n d stated that " I t is a n t i c i p a t e d that t h e
precise definitions o f the g r o u p s a n d s u b g r o u p s a n d
t h e i r n a m e s will e v o l v e a n d c h a n g e w i t h t i m e . "
The AIPEA Nomenclature Committee (Bailey
1980) rejected t e r m s s u c h as " k a n d i t e " or " s e p t e c h l o r i t e " as a l t e r n a t i v e g r o u p a n d s u b g r o u p n a m e s for
k a o l i n i t e or s e r p e n t i n e , respectively, a n d these t e r m s
s h o u l d n o t b e used. Interestingly, the A I P E A N o m e n clature C o m m i t t e e u s e d the t e r m " k a o l i n " interc h a n g e a b l y w i t h " k a o l i n i t e " g r o u p in the text o f the
r e p o r t (Bailey 1980, p. 86), as d i d the report o f the
C M S N o m e n c l a t u r e C o m m i t t e e ( M a r t i n et al. 1991,
Table 1). H o w e v e r , the u s e o f " k a o l i n " as the g r o u p
n a m e was a p p a r e n t l y n e v e r d i s c u s s e d b y either c o m mittee.
Studies of t h e k a o l i n i t e - s e r p e n t i n e g r o u p m i n e r a l s
(for e x a m p l e , E h r e n b e r g et al. 1993) s u g g e s t the n e e d
for a g r o u p n a m e that differs f r o m the species n a m e ,
since authors u s e the t e r m " k a o l i n i t e " to refer to a n y
o f the 3 polytypes: kaolinite, nacrite or dickite. " K a o l i n " w a s defined (see K u z v a r t 1977) at t h e T h i r d Ka-
It is the r e c o m m e n d a t i o n o f this c o m m i t t e e that the
t e r m " k a o l i n - s e r p e n t i n e " g r o u p b e u s e d to d e s i g n a t e
w h a t w a s p r e v i o u s l y r e f e r r e d to as t h e " k a o l i n i t e - s e r p e n t i n e " group, as s h o w n in Table 1. T h e C o m m i t t e e
b e l i e v e s that little c o n f u s i o n will r e s u l t in the u s e o f
" k a o l i n " , since the d i s t i n c t i o n o f " k a o l i n " as a r o c k
t e r m or as a m i n e r a l g r o u p n a m e is r e c o g n i z a b l e b y
context.
COMMERCIAL
NAMES AND SYNTHETIC
MATERIAL
Commercially available synthetic material must be
explicitly r e f e r r e d to as a c o m m e r c i a l n a m e in quotations and, i f the n a m e is r e c o r d e d as a t r a d e m a r k , capitalized. T h u s , for a h y p o t h e t i c a l h e c t o r i t e - l i k e m a t e rial, " X y z i t e " , the n a m e o f w h i c h h a s b e e n r e c o r d e d
as a t r a d e m a r k , t h e a p p r o p r i a t e r e f e r e n c e i n a public a t i o n s h o u l d read: " X y z i t e ' " (a s y n t h e t i c hectoritelike material, X y z M a n u f a c t u r i n g Co., C h i c a g o , Illinois, U S A ) . S y n t h e t i c m a t e r i a l s h o u l d b e r e f e r r e d to
as " h e c t o r i t e - l i k e " a n d n o t " h e c t o r i t e " , b e c a u s e the
latter implies a naturally occurring m i n e r a l . B e c a u s e
the t e r m " s y n t h e t i c " is u n a m b i g u o u s , specifically negates the n a t u r a l l y o c c u r r i n g aspect o f the m i n e r a l
c h a r a c t e r i s t i c in q u e s t i o n a n d is c o m m o n l y used, the
u s e o f " s y n t h e t i c " as a d e s c r i p t i o n m o d i f i e r to a m i n eral n a m e (for e x a m p l e , " s y n t h e t i c q u a r t z " ) is acceptable. T h e issue o f the use o f " s y n t h e t i c " h a s rec e n t l y b e e n d i s c u s s e d b y the I M A (Nickel 1996), a n d
the a b o v e u s a g e is c o n s i s t e n t w i t h t h e s e r e c o m m e n dations.
REFERENCES
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Brindley GW. 1967. CIPEA Nomenclature Subcommittee,
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Ehrenberg SN, Aagaard R Wilson MJ, Fraser AR, Duthie
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(Received 4 February 1997; accepted 31 March 1997; Ms.
97-014)