mayenite supergroup, part i: recommended nomenclature

Mayenite supergroup, part I: Recommended nomenclature

EVGENY V. GALUSKIN1,*, FRANK GFELLER2, IRINA O. GALUSKINA1, THOMAS ARMBRUSTER2, RADU BAILAU1 andVIKTOR V. SHARYGIN3,4

1 Faculty of Earth Sciences, Department of Geochemistry, Mineralogy and Petrography, University of Silesia, Bedzinska60, 41–200 Sosnowiec, Poland

*Corresponding author, e-mail: [email protected] Mineralogical Crystallography, Institute of Geological Sciences, University of Bern, Freiestrasse 3, 3012 Bern,

Switzerland3 V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk,

630090, Russia4 Russia and Department of Geology and Geophysics, Novosibirsk State University, Pirogova Street 2, Novosibirsk

630090, Russia

Abstract: The mayenite supergroup, accepted by the IMA-CNMNC (proposal 13-C), is a new mineral supergroup comprising twogroups of minerals isostructural with mayenite (space group No. 220, I43d, a ! 12 A) with the general formulaX12T14O32"x(OH)3x[W6"3x]: the mayenite group (oxides) and the wadalite group (silicates), for which the anionic charge over 6 Wsites is "2 and "6, respectively. Currently only minerals dominated by end-members with x ¼ 0 and the simplified formulaX12T14O32[W6] have been reported. The mayenite group includes four minerals: (1) chlormayenite, Ca12Al14O32[&4Cl2]; (2)chlorkyuygenite, Ca12Al14O32[(H2O)4Cl2]; (3) fluormayenite, Ca12Al14O32[&4F2]; and (4) fluorkyuygenite, Ca12Al14O32[(H2O)4

F2]. The wadalite group comprises the two mineral species wadalite, with the end-member formula Ca12Al10Si4O32[Cl6], andeltyubyuite, with the end-member formula Ca12Fe3þ

10Si4O32[Cl6]. Current research on minerals and synthetic compoundsindicates that minerals close to the composition of ideal end-members, such as Ca12Fe3þ

10Si4O32[F6], Ca12Si9Mg5O32[Cl6] andCa12Al14O30(OH)6[&6], could be found in Nature.

A detailed re-examination of the type specimens of mayenite, originally described as Ca12Al14O33, indicates thatCa12Al14O32[&4Cl2] is its correct end-member formula. Consequently, we are redefining and renaming mayenite as chlormayenite,Ca12Al14O32[&4Cl2], whereas the name mayenite would be reserved for a potential mineral with the end-member compositionCa12Al14O32[&5O]. As a consequence, the mineral brearleyite, Ca12Al14O32[&4Cl2], described in 2011 is identical with chlormaye-nite and is therefore discredited. By analogy with chlormayenite we changed the name of kyuygenite into chlorkyuygenite.

Key-words: mayenite supergroup nomenclature; mayenite group; wadalite group; chlormaynite; fluormayenite; chlorkyuygenite;fluorkyuygenite; eltyubyuite; brearleyite; calcium aluminate.

Introduction

Since 2010, five minerals related to mayenite,Ca12Al14O32[&5O] or Ca12Al14O33, (Hentschel, 1964),and wadalite, Ca12Al10Si4O32[Cl6] or Ca12Al10Si4O32

Cl6 (Tsukimura et al., 1993), have been described: brear-leyite, Ca12Al14O32[&4Cl2] (IMA2010-062; Ma et al.,2011); eltyubyuite, Ca12Fe3þ

10Si4O32[Cl6] (IMA2011-022; Galuskin et al., 2013; Gfeller et al., 2015); kyuygen-ite (chlorkyuygenite, see below), Ca12Al14O32[(H2O)4

Cl2] (IMA2012-046; Galuskin et al., 2015a); fluormaye-nite, Ca12Al14O32[&4F2] (IMA2013-019; Galuskin et al.,2015b); and fluorkyuygenite, Ca12Al14O32[(H2O)4F2](IMA2013-043; Galuskin et al., 2015b). Structural stu-dies (Tsukimura et al., 1993; Mihajlovic et al., 2004;

Galuskin et al., 2012b, 2015a and 2015b; Gfeller et al.,2015) show that all these minerals are closely relateddespite belonging to different classes (oxides and sili-cates), and thus naturally constitute a group. The struc-tures of mayenite and related minerals resemble thestructures of katoite–grossular solid solutions, but theminerals differ in that octahedral sites are not alwayspresent, so minerals isostructural with mayenite andwadalite were not taken into consideration when prepar-ing the new garnet supergroup nomenclature (Grewet al., 2013). All new mineral discoveries listed aboverequired a classification of minerals with the mayenite-type structure. Thus, an informal working group wascreated with the aim solving this task. Subsequently,this group devised a nomenclature of the mayenite

0935-1221/15/0027-2418 $ 5.85DOI: 10.1127/ejm/2015/0027-2418 # 2014 E. Schweizerbart’;sche Verlagsbuchhandlung, D-70176 Stuttgart

Eur. J. Mineral.2015, 27, 99–111Published online 3 December 2014

eschweizerbart_xxx

supergroup, which was approved by CNMNC IMA inMarch 2014 (proposal 13-C; Williams et al., 2014).

The present paper is the first part of the series of paperson the mayenite supergroup minerals. The second paper ofthis series describes the new mineral chlorkyuygenite(Galuskin et al., 2015a), whereas the third paper providesdescriptions of the two new minerals fluormayenite andfluorkyuygenite from holotype specimens, collected at theJabel Harmun, Judean Mts., Palestinian Autonomy andfrom the Hatrurim Basin, Negev Desert, Israel, respectively(Galuskin et al., 2015b). In the fourth paper we present newX-ray single-crystal structure data for eltyubyuite (Gfelleret al., 2015).

The synthetic analogue of mayenite is an importantcomponent of cement where it is known as calcium alumi-nate, 12CaO%7Al2O3, long before its discovery as a mineral(Bussem & Eitel, 1936). The structure of mayenite, spacegroup I43d, a! 12 A, was first determined using syntheticmaterial by Bussem & Eitel (1936). Unusual physical andchemical properties of mayenite are related to its largezeolite-like cages (Bartl & Scheller, 1970; Boysen et al.,2007). The mayenite structure contains 32 framework oxy-gens linked to calcium and aluminium and a ‘‘free’’, 33rd

oxygen disordered over the six cages and easily mobilizedfrom one cage to another (Matsuishi et al., 2009; Boysenet al., 2010; Janek & Lee, 2010; Hayashi, 2011). Thus,synthetic mayenite, Ca12Al14O32[&5O], is actually ananion conductor. This migrating oxygen anion has thecharacteristics of a radical, which explains rapid hydrationor hydroxylation in a humid environment (e.g. Raab &Pollman, 2011). Kurashige et al. (2008) reported a uniquecase in which the oxygen in the cages was ordered and thesymmetry reduced to I42m in mayenite crystals grown bythe Czochralski method. In chlorine-bearing mayenite(chlormayenite, see below), Ca12Al14O32[&4Cl2], oxygenand one vacancy in the cages are replaced by two Cl",which are coordinated by two Ca2þ (Fig. 1).

In the main section of this paper we present: (1) a reviewof recent crystallographic studies leading to a new struc-tural formula for mayenite and related minerals, (2) aredefinition of mayenite and discreditation of brearleyitebased on a reinvestigation of the holotype specimen andadditional samples from the type locality, (3) renaming ofkyuygenite, and (4) basic concepts for the classification ofmayenite and related minerals with practical guidelines forits application. In addition, we propose a mayenite super-group comprising the mayenite group (oxides) and thewadalite group (silicates), consistent with the hierarchyof mineral groupings advocated by Mills et al. (2009).

Structure and crystal-chemical formula ofmayenite and related minerals

The structure of minerals of the mayenite supergroup isbased on a tetrahedral framework {T14O32}, which formssix structural cages (Bussem & Eitel, 1936). Depending onthe type of tetrahedrally coordinated cations in the

framework (T¼ Al3þ, Fe3þ, Mg2þ, Si4þ Ti4þ), the negativeframework charge ranges between –18 and –22. Each of thestructural cages is occupied by two Ca2þ (þ24), whichresults in an excess positive charge ranging between þ2(mayenite group) and þ6 (wadalite group). The charge isbalanced by anions at the central [W] site of the structuralcages (Fig. 1).

Fig. 1. Overall view of chlormayenite structure. Chlorine (greensphere) coordinated by two calcium cations (pale spheres). Thetwo different types of aluminum tetrahedra are distinguished bylight- and dark blue colour. Oxygen sites shared by two AlO4 tetra-hedra are grey whereas oxygen sites only bonded to one tetrahedronare in black.

100 E.V. Galuskin et al.

eschweizerbart_xxx

A more general crystal chemical formula of mineralswith the mayenite-type structure can be written as:X12{IVT18"x

VIT’1x}IVT26O124O28"x(O2aH)3x[W6"3x](Galuskin et al., 2012a and 2012b), where x¼ 0–2, X is Capolyhedral; T1 and T’1 (modified T1 site) are distortedtetrahedral and octahedral sites, respectively, centered byAl and other cations such as Fe3þ, Mg, Ti, Si . . . ; T2 is aregular tetrahedron filled by Al, Si and Fe3þ. The W site isconfined to the centre of a structural cage & 5 A in dia-meter (Sakakura et al., 2011). But this generalized formulais not practical to use for classifying minerals related tomayenite because of the large uncertainties in distinguish-ing the cation occupancies of the tetrahedral T1 and T2sites. For example, Si in wadalite can occupy either T1 orT2 (Tsukimura et al., 1993; Fujuta et al., 2001; Mihajlovicet al., 2004). Instead we propose to use a simplified crystalchemical formula, X12T14O32"x(OH)3x[W6"3x], with thecombined tetrahedral sites T1 and T2. In the absence of adirect determination of H2O, formulae for mayenite andrelated minerals have been calculated from chemical ana-lyses assuming 26 total cations, O2aOH as 3 ' [(!cationcharge – 64) – (Cl þ F þ OH)] ! 3 ' [2– (Cl þ F þ OH)](only for a weakly hydroxylated phase; Galuskin et al.,2012b), WOH from charge balance, and H2O as 6 – (Fþ Clþ OH) [for a highly hydrated phase]. At present, onlycompositions dominated by end-members with x ¼ 0,i.e., X12T14O32[W6] are known as minerals.

Renaming of mayenite as chlormayenite

Hentschel (1964) introduced mayenite as the calcium alu-minate, 12CaO%7Al2O3 or Ca12Al14O33, which he namedfor Mayen, a town near the type locality of EttringerBellerberg, Eifel, Germany, where mayenite occurs inaltered calcsilicate xenoliths in volcanic rock. His pro-posed formula was based on analogy with the syntheticcompound, which had been well studied as a component ofcement clinker (e.g., Bussem & Eitel, 1936). However,Hentschel (1964) admitted his wet-chemical analysis wasunsatisfactory due the paucity and impurity of the analyzedmaterial. Hentschel (1987) reported new analyses

containing several wt. % Cl and suggested that mayenitecould be a solid solution between Ca12Al14O33 andCa12Al14O32Cl2. It is important to note that the oxideCa12Al14O33 is highly reactive in the presence of H2Oand decomposes rapidly by forming hydrates of calciumaluminates like Ca2AlO5%8H2O or CaAlO4%10H2O (Raab& Pollman, 2011). Thus, preservation of Ca12Al14O33 atthe type locality, given its association with ettringiteCa6Al2(SO4)3(OH)12(H2O)26 and portlandite Ca(OH)2

(Hentschel, 1987), seems highly unlikely.We studied the holotype specimen No. M5026/86 from

the Mineral Museum, University of Cologne, Germany anda type specimen, No. 120045, of mayenite and brownmil-lerite from the National Museum of Natural History,Washington, D.C., USA. Both are fragments of an alteredcarbonate xenolith from the Ettringer-Bellerberg volcano.In the holotype specimen M5026/86 mayenite occurs asgrains up to 80–100 mm in size within a larnite zonecontaining abundant brownmillerite and rare ternesitecrystals (Fig. 2). Secondary minerals include katoite–gros-sular, ettringite, and afwillite. In addition, mineral speciesdiscovered decades after mayenite (e.g., jasmundite, lakar-giite, srebrodolskite, shulamitite, ye’elimite) were found inother zones of this sample (e.g. Sharygin et al., 2013).

Most of the type specimen No. 120045 is composed of alow-temperature mineral association (katoite–grossular,ettringite, afwillite, jennite, portlandite) with relics ofbrownmillerite and mayenite completely replaced by katoi-te–grossular. Mayenite up to 20 mm across is preserved onlyin grey fragments of rock together with spurrite, larnite,hydroxylellestadite, and brownmillerite (Fig. 3). Spurritemay indicate that specimen No. 120045 belongs to thecentral part of the mayenite-bearing xenolith.

We did not attempt to fully investigate the holotypemayenite, but instead compared holotype mayenite withthe mayenite from the type locality, for which compositionand structural data were obtained (Galuskin et al., 2012b).Raman spectra of these mayenite samples are practicallyidentical (Fig. 4). The empirical crystal chemical formula ofholotype mayenite (M5026/86), Ca11.996(Al13.572Fe3þ

0.418

Si0.007Mg0.006)!14.003(O31.375&0.625)!32(&4.124 (OH)1.876)

!6[Cl1.375&4.625]!6 (Table 1, analysis 1), and type mayenite

Fig. 2. A. Holotype specimen M5026/86, Mineral Museum, University of Cologne, Germany. Greenish zone (upper fragment of specimen) isenriched in chlormayenite crystals up to 100 mm in size; B. Backscattered-electron image of the polished mount prepared from the greenishzone. Lrn - larnite, May - chlormayenite, Brm - brownmillerite, Trn - ternesite.

Mayenite supergroup nomenclature 101

eschweizerbart_xxx

(No. 120045), (Ca12.069Mn2þ0.004)!12.073(Al13.324Fe3þ

0.562

Mg0.022Si0.015 Ti4þ0.004)!13.931(O31.249&0.751)!32 (&3.747

(OH)2.253)!6 [Cl1.172&4.828]!6 (Table 1, analysis 2), arevery close to the composition of type-locality mayenite(Bernd Ternes’ sample), Ca12(Al13.513Fe3þ

0.465 Mg0.012

Si0.007Ti4þ0.003)!14 (O31.323&0.677)!32(&3.972(OH)2.028)!6

[Cl1.323&4.680]!6 (Galuskin et al., 2012b). The composi-tions of holotype, type and type-locality mayenite may bedescribed as sum of two main end-members, respectively,69 %, 59 % and 62.5 %, Ca12Al14O32[&4Cl2], 31 %, 41 %and 37.5 % Ca12Al14O30(OH)6(&6); the end-memberCa12Al14O32[&4Cl2], therefore, is dominant. There isno need for the end-member Ca12Al14O32[&5O][IMA_Master_List (2014–03)] proposed by Hentschel(1964, 1987) to explain compositional variations of maye-nite in specimens from the type locality, including the

holotype and type material, i.e., Hentschel’s (1987) sugges-tion that mayenite belongs to an anhydrous solid solutionbetween Ca12Al14O32[&5O] and Ca12Al14O32[&4Cl2]could not be confirmed (Galuskin et al., 2012b).

Instead, our investigations have shown that hydroxylplays an important role in mayenite from the type locality(Galuskin et al., 2012b). Mayenite apparently formedinitially as the anhydrous phase Ca12Al14O32[&4Cl2],but was subsequently partially hydroxylated to formsolid solutions between Ca12Al14O32[&4Cl2] andCa12Al14O30(OH)6(&6). This conclusion is supported bythe discovery of mayenite close to the end-memberCa12Al14O32[&4Cl2] as inclusions in jasmundite,Ca11(SiO4)4O2S, from an altered carbonate xenolith involcanic rocks of the Caspar quarry near Mayen, Eifeldistrict, Germany (Table 1, analysis 3, Bernd Ternes’ sam-ple). The component Ca12Al14O30(OH)6(&6) is character-ized by a coordination change of Al from tetrahedral tooctahedral, associated with additional OH groups. Chargebalance is attained by the presence of OH", which isevident in Raman spectra (Fig. 4).

On the basis of these results mayenite should be rede-fined as Ca12Al14O32[&4Cl2] and renamed chlormayenite.More generally, we propose to add a prefix to indicateanion composition, at the same time retaining the rootname for the town near the type locality. By analogy, themayenite-group mineral from Hatrurim, Israel, with theend-member formula Ca12Al14O32[&4F2], is named fluor-mayenite (see below). The root name mayenite without aprefix should be reserved for a mineral with the composi-tion Ca12Al14O32[&5O] if such be found. Changing theformula for mayenite as a mineral species could lead toconfusion when information is exchanged between miner-alogists and other scientists. In addition, the root namemayenite is appropriate as a group name for oxides iso-structural with Ca12Al14O32[&5O] and chlormayenite.

Chesnokov & Bushmakin (1995) were the first to use thename ‘‘chlormayenite,’’ which they applied to an anthro-pogenic phase formed in burned dumps of the Chelaybinskcoal Basin, Russia. However, their simplified crystal che-mical formula (Ca13Al14(SiO4)0.5O32Cl2) for this phase,calculated from wet chemical analysis, is erroneous.Recalculation of Chesnokov et al.’s data, supported by

Fig. 3. A. Type specimen No. 120045, National Museum of Natural History, Washington, D.C., USA. Grey fragments of rock are enriched inchlormayenite crystals less than 20 mm in size; B. Backscattered-electron image of the polished mount prepared from the grey fragment ofrock indicated by the arrow in Fig. 2A (BSE), Ell - hydroxylellestadite, Lrn - larnite, May – chlormayenite, Brm - brownmillerite, Spu -spurrite.

Fig. 4. A. Raman spectra of chlormayenite from Eifel: 1–type-locality chlormayenite (Bernd Ternes’ [cf. 4/5] sample), 2–holotypechlormayenite (M5026/86), 3–type chlormayenite (120045). B.Raman spectrum of chlorkyuygenite from Upper Chegem Caldera.Spectrum 1 was obtained using Dilor XY Raman spectrometer (514nm), spectrum 2, 3 and chlorkyuygenite spectrum were obtainedusing WITec confocal CRM alpha 300 Raman microscope (532nm). a.u. – arbitrary units.


eschweizerbart_xxx

Tab

le1

.C

hem

ical

com

po

siti

on

of

may

enit

e-su

per

gro

up

min

eral

s:ty

pe

chlo

rmay

enit

e,E

ifel

(1-

M5

02

6/8

6,2

-N

o.1

20

04

5),

chlo

rmay

enit

ein

clu

sio

ns

fro

mja

smu

nd

ite,

Eif

el(3

),fl

uo

rmay

enit

e,Je

bel

Har

mu

n(4

),fl

uo

rky

uy

gen

ite,

Hat

ruri

mB

asin

(5),

chlo

rmay

enit

e,H

atru

rim

Bas

in(6

),h

igh

chlo

rin

efl

uo

rmay

enit

e,H

atru

rim

Bas

in(7

),ch

lork

yu

yg

enit

e,H

atru

rim

Bas

in(8

),h

igh

chlo

rin

ech

lorm

ayen

ite,

Eif

el(9

)an

dan

tro

po

gen

icF

-an

alo

gu

eo

fel

tyu

by

uit

e,C

hel

yab

insk

coal

bas

in(1

0),

wt.

%.

12

34

56

78

910

mea

n40

s.d.

range

mea

n11

s.d.

range

mea

n14

s.d.

range

mea

n12

s.d.

range

mea

n14

s.d.

range

mea

n3

mea

n32

s.d.

range

SiO

20.0

30.0

2,

0.0

2–0.0

60.0

60.0

30.0

3–0.1

20.0

20.0

2,

0.0

2–0.0

70.0

40.0

20.0

2–0.0

80.8

90.4

0.4

4–1.4

10.3

50.0

60.3

60.7

211.0

60.5

9.9

2–11.8

4T

iO2

,0.0

20.0

20.0

2,

0.0

2–0.0

60.0

10.0

1,

0.0

2–0.0

4,

0.0

10.0

40.0

3,

0.0

2–0.1

2,

0.0

20.0

6,

0.0

2A

l 2O

347.7

80.4

46.9

–48.6

46.6

00.6

45.7

–47.4

46.5

00.4

45.9

–47.4

48.8

50.2

48.2

–49.1

45.0

00.3

44.4

–45.4

48.1

348.1

445.5

641.0

1,

0.0

3F

e 2O

32.3

10.3

1.7

6–2.8

43.0

80.3

2.6

1–3.5

02.0

60.2

1.7

7–2.3

71.5

10.1

1.3

2–1.7

52.1

00.4

1.5

9–2.6

80.8

72.2

81.9

76.8

844.5

60.9

42.7

–47.0

MnO

,0.0

60.0

20.0

2,

0.0

6–0.0

60.0

20.0

20.0

2–0.0

8,

0.0

6,

0.0

6,

0.0

60.0

80.1

,0.0

6–0.6

0M

gO

0.0

20.0

2,

0.0

2–0.0

60.0

60.0

20.0

2–0.0

9,

0.0

10.1

10.0

20.0

8–0.1

5,

0.0

10.0

3,

0.0

10.0

20.0

60.1

,0.0

1–0.5

2C

aO46.4

50.3

45.5

–47.1

46.4

30.6

45.5

–47.3

46.3

90.4

45.8

–47.0

47.5

70.1

47.4

–47.8

44.6

40.3

44.0

–45.2

46.0

46.9

44.4

43.6

037.2

40.6

35.8

–38.6

SrO

,0.0

6,

0.0

7,

0.0

6,

0.0

5,

0.0

50.1

10.0

6,

0.0

6n.m

.N

a 2O

,0.0

2,

0.0

2,

0.0

10.0

80.0

10.0

6–0.1

0,

0.0

1,

0.0

20.1

10.0

2,

0.0

2S

O3

,0.0

3,

0.0

3,

0.0

30.0

80.0

30.0

4–0.1

2,

0.0

40.0

70.0

80.0

60.2

40.1

0.0

6–0.4

9P

2O

5,

0.0

3,

0.0

3,

0.0

3,

0.0

3,

0.0

30.1

3,

0.0

4,

0.0

4n.m

.C

l3.3

70.2

3.0

5–3.8

02.8

50.1

2.6

4–3.0

24.1

40.4

3.4

5–4.7

40.1

10.0

10.0

9–0.1

2,

0.0

34.0

41.9

83.9

76.9

10.0

20.0

2,

0.0

2–0.0

7F

,0.1

2,

0.1

3,

0.1

02.1

30.2

1.8

4–2.4

52.3

80.3

1.8

4–2.8

40.2

41.1

80.3

00.6

410.8

30.5

10.0

3–11.5

9H

2O

1.1

71.3

90.1

90.5

14.7

10.4

40.5

24.7

3"

O¼

Fþ

Cl

0.7

60.6

40.9

30.9

21.0

01.0

10.9

41.0

21.8

34.5

7

100.3

699.8

798.4

0100.0

698.7

699.4

100.4

100.4

98.0

199.5

2F

orm

ula

sca

lcula

ted

for

tota

lca

tions¼

26

Ca

11.9

96

12.0

69

12.1

80

12.0

37

12.0

31

11.9

46

11.9

68

11.9

86

12.0

23

12.2

29

Sr

0.0

15

0.0

08

Na

0.0

37

0.0

51

0.0

10

X11.996

12.069

12.180

12.073

12.031

11.962

12.027

11.996

12.023

12.229

Al

13.5

72

13.3

24

13.4

29

13.5

96

13.3

40

13.7

55

13.5

24

13.5

29

12.4

40

Fe3þ

0.4

18

0.5

62

0.3

80

0.2

68

0.3

97

0.1

59

0.4

09

0.3

74

1.3

33

10.2

77

Si

0.0

07

0.0

15

0.0

05

0.0

09

0.2

24

0.0

85

0.0

14

0.0

91

0.1

85

3.3

90

Ti

0.0

04

0.0

02

0.0

08

0.0

12

Mn

2þ

0.0

04

0.0

04

0.0

21

Mg

0.0

06

0.0

22

0.0

39

0.0

11

0.0

08

0.0

27

S6þ

0.0

14

0.0

13

0.0

14

0.0

11

0.0

55

P0.0

27

T14.003

13.931

13.820

13.927

13.969

14.038

13.973

14.004

13.977

13.771

Cl

1.3

75

1.1

72

1.7

19

0.0

44

1.6

60

0.8

00

1.6

95

3.0

14

0.0

10

F1.5

91

1.8

93

0.1

84

0.8

90

0.2

39

0.5

21

10.4

98

H2O

*3.7

96

3.8

82

OH

**

0.3

10

0.1

85

W1.375

1.172

1.719

1.635

6.000

1.844

1.689

6.001

OH

***

1.8

76

2.2

53

0.3

12

0.7

95

0.3

10

0.7

12

0.8

34

0.1

85

Footnotes:

*H

2O

wt.

%ca

lcula

ted

from

OH

*pfu

(cal

cula

ted

on

char

ge

bal

ance

)an

dH

2O

**

pfu

[cal

cula

ted

as6

–(C

lþO

H)]

or

from

OH

***

pfu

(cal

cula

ted

as3'

[(P

cati

on

char

ge

–64)

–(C

lþFþ

OH

)])

(see

Gal

usk

inetal.

,2012b);

n.d

.–

not

det

ecte

d;

n.m

.–

not

mea

sure

d.

All

Fe

isgiv

enas

Fe 2

O3.


eschweizerbart_xxx

our unpublished analytical results of Cl-bearing mineralsfrom the burned dumps of the Chelyabinsk coal Basin(samples were kindly supplied by M. Murashko), confirmsthat this anthropogenic phase is analogous to Si- and Mg-bearing chlormayenite.

Renaming of kyuygenite

By analogy with chlormayenite (Ca12Al14O32[&4Cl2]),fluormayenite (Ca12Al14O32[&4F2]) and fluorkyuygenite(Ca12Al14O32[(H2O)4F2]), the name of kyuygenite,Ca12Al14O32[(H2O)4Cl2], found in xenoliths within ignim-brites of the Upper Chegem Caldera, Kabardino-Balkaria,Russia, is changed to chlorkyuygenite. Its full descriptionis presented in the accompanying paper (Galuskin et al.,2015a).

Discreditation of brearleyite

Ma et al. (2011) introduced the new species brearleyite,Ca12Al14O32Cl2, as ‘‘the Cl analogue of mayenite(Ca12Al14O33)’’ from a refractory inclusion from theNorthwest Africa 1934 CV3 carbonaceous chondrite, i.e.,the distinction between brearleyite and mayenite asdefined by Hentschel (1964) was the presence of 2Cl andone less O per formula unit. However, our reexaminationof the holotype mayenite clearly demonstrates the presenceof Cl and that the dominant component is Ca12Al14O32Cl2(Ca12Al14O32[&4Cl2]) and, consequently, brearleyite is nolonger a Cl analogue of mayenite, but identical to it.Despite the incompleteness of the original analysis, maye-nite was sufficiently well described by Hentschel (1964)that its validity is not in question, and thus has priority overbrearleyite. According to IMA-CNMNC procedures andguidelines (Nickel & Grice, 1998; Hatert et al., 2012), amineral may be discredited if it can be shown to be iden-tical to another one that has priority. Consequently, brear-leyite was discredited in favour of the name derived frommayenite, chlormayenite.

Mayenite from other localities

Gross (1977) reported mayenite from pyrometamorphicrocks of the Hatrurim formation, Israel, the second occur-rence of this mineral, and assigned the formulaCa12Al14O33. Reinvestigation of this mayenite showed itis its fluorine analogue, Ca12Al14O32[&4F2] (I43d, a ¼11.9894(2) A; Table 1, analysis 4), a new mineral species(fluormayenite, see Galuskin et al., 2015b) and the naturalanalogue of a synthetic phase (Williams, 1973; Qijun et al.,1997). Alteration of the fluorine analogue yielded a secondnew mineral – fluorkyuygenite, Ca12Al14O32[(H2O)4F2](I 43d, a !12 A, Galuskin et al., 2015b; Table 1, analysis5). Our latest investigations show that chlormayenite

(Ca12Al14O32[&4Cl2], end-member up to 83 %, Table 1,analysis 6) and chlorkyuygenite (Ca12Al14O32[(H2O)4Cl2],end-member up to 85 %, Table 1, analysis 7) are alsopresent in pyrometamorphic rocks of the HatrurimFormation, but in limited quantities, as are phases withintermediate composition between chlormayenite andfluormayenite (Table 1, analysis 8).

Chlormayenite (mayenite) was also reported in alteredxenoliths in alkali basalt from Kloch, Styria, Austria and itsformula given as Ca12Al14O33 (Exel, 1993). However,compositional data indicate that it contains up to 2.5wt.% Cl (Heritsch, 1990, and our data).

Synthetic analogues of mayenite

The name ‘‘mayenite’’ has been used by physicists, che-mists and technologists to refer to synthetic phases withcomposition Ca12Al14O33 (Matsuishi et al., 2003; Boysenet al., 2007, 2009, 2010; Palacios et al., 2007, 2008;Hosono et al., 2009; Sakakura et al., 2011; Tolkachevaet al., 2011). The halogen-bearing compounds Ca12Al14

O32Cl2 and Ca12Al14O32F2 have been synthesized(Williams, 1973; Qijun et al., 1997; Ju et al., 2006; Iwataet al., 2008; Sun et al., 2009) and were the main object ofnumerous studies in different fields from optic physics(transparent semiconductors) to cement, ceramics and sor-bents technology, which has resulted in hundreds of pub-lications (e.g., Hosono et al., 2007; Sushko et al., 2007a;Iwata et al., 2008; Li et al., 2009). The compoundCa12Al14O33 is very reactive in the presence of water(Park, 1998; Strandbakke et al., 2009), so it is likely thatin most geologic environments anhydrous mayenite isstabilized by halogens.

The crystal structure of synthetic mayenite is consideredas a tetrahedral framework {Al14O32}22" enclosing sixstructural cages each occupied by two Ca2þ. The excesspositive (2þ) charge is balanced by partial occupancy ofthe W site, which is located between the Ca sites at thecentre of the cages. The W site may be occupied by nega-tively charged particles or ions: electrons e", O2

", O22",

O", S2", OH", Nx", F", Cl", Au" (Posch et al., 2004;

Sango, 2006; Hosono et al., 2007; Palacios et al., 2007;Sushko et al., 2007b; Li et al., 2009; Matsuishi et al., 2009;Boysen et al., 2010; Janek & Lee, 2010) as well asuncharged molecules like H2O (Galuskin et al., 2015aand 2014b). The first synthetic wadalite had the composi-tion Ca12Al10.6Si3.4O32C15.4 (Feng et al., 1988). The syn-thetic analogues of wadalite Ca12Al10Si4O32Cl6 andCa12Al10Si4O32O3 are also known (Fujita et al., 2003,2005; Sato et al., 2006).

Unit-cell volume, density, and refractive index are com-pared for synthetic and natural mayenite related species(Table 2). It is striking that all values determined byHentschel (1964) for his original mayenite are signifi-cantly different from those for Ca12Al14O33 and chlor-kyuygenite (Galuskin et al., 2013, 2015a). Instead,


eschweizerbart_xxx

Hentschel’s (1964) values agree with those obtained onCa12Al14O32Cl2 and type-locality mayenite by Galuskinet al. (2012b).

New nomenclature

We propose to base the classification of the mayenitesupergroup on the positive charge of the framework,balanced by anions at theW site, i.e., the boundary betweenthe mayenite and wadalite groups is a total charge of 4 over6 W sites (Figs. 5 and 6; Table 3). End-members of themayenite group would have a total charge of 2 over 6 Wsites, whereas end-members of the wadalite group wouldhave a total charge of 6 over 6 W sites. The boundarycorresponds to 2 Si atoms per formula unit (apfu) at the Tsites (Fig. 6). In a given group, mineral species would bedistinguished on the basis of the anion dominant at the Wsite, whether Cl, F (þ OH or O). Further distinction ofmineral species in the mayenite group is based on thepresence of H2O versus vacancy at W.

In the original description of wadalite, the end-membercrystal-chemical formula Ca6Al5Si2O16Cl3 was proposed(Tsukimura et al., 1993; Ishii et al., 2010; IMA List ofMinerals - March 2014). Taking into consideration theproposed general formula of minerals of the mayenitesupergroup, the wadalite formula should be doubled toCa12Al10Si4O32[Cl6].

The most important substitutions in minerals of themayenite supergroup are the following:

(1) T(Al,Fe3þ)þ W&, TSi4þþ W(Cl",F"), which relateschlormayenite and fluormayenite, with wadalite andits Fe3þ analogue, eltyubyuite. This substitution isexpressed as a linear array of compositions betweenSi ¼ 0, Cl ¼ 2 and Si ¼ 4 and Cl ¼ 6 (Fig. 5).

(2) TAl3þ , TFe3þ, which relates wadalite and eltyu-byuite (Fig. 6).

(3) W&, WH2O, which relates chlormayenite and fluor-mayenite with chlorkyuygenite and fluorkyuygenite,respectively

(4) The substitution F",Cl" is most distinctly displayedin the minerals of the chlormayenite–fluormayeniteseries from pyrometamorphic rocks of the Hatrurim

Formation (Table 1, analysis 8). The significant dif-ference between the ionic radii of fluorine and chlorineresults in a small shift of Ca towards F, as reported byGaluskin et al. (2015b).

Other substitutions could also be relevant for distinguish-ing mineral species in the mayenite supergroup, but to datehave not yielded any additional mineral species:

(5) 2T(Al3þ, Fe3þ) , TMg2þþ T(Si4þ, Ti4þ), which mostoften is noted in wadalite-group minerals. Maximum Mgcontents reach 2 apfu, and Si ! 6 apfu, i.e., the formulabecomes Ca12(Mg2Al6Si6)O32[Cl6], which significantlyexceeds the Si content in the wadalite end-member (Figs.5 and 6). Nonetheless, Mg-bearing wadalite is not adistinct species because the two T sites are to be consid-ered together for classification purposes. If the individualoccupancies of the T1 and T2 sites were considered thebasis of classification, the structures would have to berefined, and occupancies of individual T sites measuredin each specimen in order to name it. The formula of anAl-free member of the wadalite group, where all Al issubstituted by Mg and Si, is Ca12(Si9Mg5)O32[Cl6]. Onfirst consideration, such a composition appears not to bestable as a mayenite-supergroup mineral because Mgwould be expected to occupy the relatively large andmore distorted tetrahedra T1 (8 apfu) and Si, the rela-tively small, nearly ideal tetrahedra T2 (6 apfu) (Fujitaet al., 2001), so that the maximum Mg content would beCa12

T1(Al6Mg2)T2(Si6)O32[Cl6]. Only two of the ana-

lyses of wadalite in our compilation contain more than6 Si apfu (Figs. 5 and 6), suggesting the upper limit on Siis 6 apfu in minerals of the wadalite group. However, thelatest experimental data on synthesis of high-Mg wada-lite have revealed that tetrahedra can change their func-tions in the mayenite structure, such that T1 acceptssmaller cations and T2 larger cations (Gfeller, unpub-lished data). Gfeller (unpublished data) synthesizedphases with the compositions betweenCa12

T1(Si8)T2(Mg4.5Al1.5)O32[Cl5.5&0.5] and Ca12

T1

(Si8)T2(Mg4Al2)O32[Cl6]. This suggests potential exis-

tence of a new mineral belonging to the wadalite groupwith a composition between Ca12(Si6Al6Mg2)O32[Cl6]and Ca12(Si8Al2Mg4)O32[Cl6], leading to a new mineralspecies in the wadalite group with a theoretical end-

Table 2. Physical properties of some mayenite related compounds.

Formula Ca12Al14O33 Ca12Al14O32Cl2

‘‘Mayenite’’original

Chlormayenite, typelocality

Chlorkyuygenite, typelocality

Cell volume A3 1719.1 (m) 1732.1 (m) 1736.7 (m) 1741.9 (m) 1740.3 (m)Density g/cm3 2.70 (m) 2.79 (c) 2.85 (m) 2.77 (c) 2.95 (c)Refractive index 1.604 (m) 1.643 (m) 1.672 (m)References Boysen et al. (2007);

Kuhl (1958)Iwata et al. (2008) Hentschel (1964) Galuskin et al.

(2012b)Galuskin et al. (2015a)

Note: (m) ¼ measured, (c) ¼ calculatedChlorkyuygenite: Ca11.98(Al12.99Fe3þ

0.82Si0.18Ti4þ0.03)!14.02 (O31.91(OH)0.09)!32[(H2O)3.57Cl2.33]!6

Chlormayenite, type locality: Ca12(Al13.513Fe3þ0.465Mg0.012Si0.007Ti4þ0.003)!14 (O31.323&0.677)!32(&3.972(OH)2.028)!6 [Cl1.323&4.680]!6


eschweizerbart_xxx

member formula Ca12(Si9Mg5)O32[Cl6]. About 40 % ofthis end-member has been reported in wadalite from theAllende chondrite (Kanazawa et al., 1997; Ishii et al.,2010) and from the Caucasus (Bailau et al., 2012; ourunpublished data; Figs. 5 and 6).

(6) O2" þ Cl"/F" , 3(OH)", was first reported toexplain partial hydroxylation of chlormayenite andfluormayenite (Galuskin et al., 2012b, 2015b). Fullyhydroxylated mayenite is a possible new mineral withthe formula Ca12Al14O30(OH)6[&6], which has 0

Table 3. Mayenite-supergroup minerals.

Mayenite supergroup T site W site Formula Simplified formula

Mayenite group (Wcharge ¼ –2)1. chlormayenite Al14 &4Cl2 Ca12Al14O32 [&4Cl2] Ca12Al14O32Cl22. fluormayenite Al14 &4F2 Ca12Al14O32[&4F2] Ca12Al14O32F2

3. chlorkyuygenite Al14 (H2O)4Cl2 Ca12Al14O32[(H2O)4Cl2]4. fluorkyuygenite Al14 (H2O)4F2 Ca12Al14O32 [(H2O)4F2]

Wadalite group (Wcharge ¼ –6)5. wadalite Al10Si4 Cl6 Ca12Al10Si4O32[Cl6] Ca12Al10Si4O32Cl66. eltyubyuite Fe3þ

10Si4 Cl6 Ca12Fe3þ10Si4O32[Cl6] Ca12Fe3þ

10Si4O32Cl6

Fig. 5. Analyses of the mayenite-supergroup minerals (A) and compositional trends (B) projected in Si–Cl apfu diagrams. 1, 2, 3–wadalite,chlorkyuygenite and eltyubyuite analyses from Upper Chegem caldera (Galuskin et al., 2009; Bailau et al., 2012; our unpublished data);4–brearleyite (Ma et al., 2011); 5–wadalite, Eifel (Mihajlovic et al., 2004); 6–holotype chlormayenite, Eifel (Galuskin et al., 2012b, ourunpublished data); 7 - high chlorine chlormayenite, Eifel; 8–holotype wadalite (Tsukimura et al., 1993); 9–wadalite, Mexico (Kanazawaet al., 1997); 10–wadalite from Allende chondrite (Ishii et al., 2010); 11–15–chlorkyuygenite, chlormayenite, fluormayenite and fluorkyuy-genite (our data), Hatrurim formation; 16–anthropogenic ‘‘demidovskite’’, Chelyabinsk coal basin (Chesnokov et al., 1996); 17–FrankGfeller’s synthetic phase; 18–anthropogenic F-rich phase close to eltyubyuite, Chelyabinsk coal basin (Sharygin, 2014); 19–anthropogenicmayenite-wadalite, Oslavany, 20–anthropogenic mayenite, Zastavka (Hrselova et al., 2013) and 21–adrianite (Ma et al., 2014b).Compositional trend: A – chlormayenite–wadalite (eltyubyuite); B – chlormayenite (chlorkyuygenite) – fluormayenite (fluorkyuygenite);C – wadalite – potentially new mineral ‘‘Mg-wadalite’’ (Gfeller, unpublished data).


eschweizerbart_xxx

charge at W, because the OH groups are not at thecentre of the cage, but replace O2 and coordinate T1(Galuskin et al., 2012b).

(7) Hydroxylation of chlormayenite and fluormayenite ispossible by the substitutions Cl" , OH" andF" , OH", which have been reported in syntheticphases (Ruszak et al., 2007). The resulting compositionwould be Ca12Al14O32[&4(OH)2]. These phases mightbe found as alteration products of water-free minerals ofthe mayenite group.

Hydroxyl groups, corresponding to the two types of hydra-tion in mayenite-group minerals, differ in band position inthe OH region on Raman spectra: OH groups incorporatedby O2"þCl", 3(OH)" yield a band at about 3670 cm"1,whereas OH groups incorporated by Cl" , OH" and F"

,OH" give a band at about 3570 cm"1 (Fig. 4; Galuskinet al., 2012b, 2015a and 2015b).

(8) There are other substitutions introducing halogen inexcess of 2 (Cl, F) in end-members of the mayenitegroup and 6 (Cl, F) in end-members of the wadalitegroup. For example, chlormayenite from a xenolithenriched in rondorfite from the Caspar quarry nearMayen, Germany (collected by Bernd Ternes) has thecomposition Ca12Al12.5Fe3þ

1.5O31.25Cl3F0.5 (Table 1, an.9), and an anthropogenic F-analogue of eltyubyuite froma burned dump of the Chelyabinsk basin, Russia has thecomposition Ca12Fe3þ

10.5Si3.5O29.5F10.5 (Table 1, an. 9;Sharygin, unpublished data). The excess halogens mightbe substituting for oxygens. Possibly the mechanism for

substitution of oxygen is similar to no. 5 above forpartially hydrated chlormayenite (see above andGaluskin et al., 2012b).

Investigations of isomorphic substitutions at the X(Ca) site inminerals of the mayenite supergroup show that Ca is domi-nant in all natural phases studied to date, although an Sranalogue of Sr12Al14O33 has been synthesized (Hayashiet al., 2008). Minor Na, Sr, Y have been reported as rareimpurities in minerals of the mayenite supergroup(Kanazawa et al., 1997; Galuskin et al., 2009; Bailau et al.,2012). Sodium could be incorporated by the substitutionNaþþAl3þ, Ca2þþMg2þ in Mg-bearing wadalite (Fig. 6).

Minor end-members noted among the minerals of themayenite supergroup and also synthetic and not strictlynatural phases are given in Table 4. The data suggest thatminerals close to the composition of the ideal end-mem-bers Ca12Fe3þ

10Si4O32[F6], Ca12Si9Mg5O32[Cl6] andCa12Al14O30(OH)6[&6] could be found in Nature.

Adrianite

After our mayenite supergroup nomenclature wasapproved by CNMNC IMA in March 2014 (proposal13-C; Williams et al., 2014), adrianite,Ca12(Al4Mg3Si7)O32Cl6, was approved in July 2014 asa new mineral species in the wadalite group (IMA2014–028; Ma et al., 2014a), and a brief description ofthe mineral was published as an abstract (Ma et al.,2014b). Adrianite is reported to occur in grains 2–6

Fig. 6. Analyses of the mayenite-supergroup minerals projected in the Fe(þMg)–Al–Si apfu diagram, symbols as in Fig. 5.


eschweizerbart_xxx

mm in size, with monticellite, grossular, wadalite, andhutcheonite in secondary alteration areas along cracksbetween primary melilite, spinel and Al,Ti-diopside inthe core area of the Allende CV3 meteorite. The struc-ture was not refined; electron backscatter diffractiondata were fitted using the wadalite structure I"43d withthe unit-cell dimensions: a ¼ 11.981 A, V ¼ 1719.8 A3,and Z ¼ 2 (Feng et al., 1988). An averaged electronmicroprobe analysis is (wt%): CaO 41.49, SiO2 27.49,Al2O3 12.42, MgO 7.34, Na2O 0.41, Cl 13.03, -O ¼ Cl–2.94, total 99.24; this analysis yields the empiricalformula (Ca11.69Na0.21)(Al3.85Mg2.88Si7.23)O32Cl5.80, ide-ally Ca12(Al4Mg3Si7)O32Cl6, which Ma & Krot (2014b)inferred to be the end-member formula. This composi-tion is plotted in our classification diagrams (Figs. 5 and6). However, this formula is not a proper end-member,because there is no way to apportion Al, Mg and Sibetween T1 and T2 so that only one site has two occu-pants and no site has more than two, e.g.,Ca12

T1(Al4Mg3Si)T2(Si6)O32[Cl6] or Ca12T1(Al3Mg3)T2

(Si7Al)O32[Cl6] (see discussion above in the chapter‘‘New nomenclature’’ concerning the 2T(Al3þ, Fe3þ), TMg2þþ T(Si4þ, Ti4þ) substitution). Pending theavailability of information on T-site occupancies, it isnot possible to specify the relationship of adrianite toother minerals in the mayenite supergroup.

Summary of conclusions, actions andrecommendations

" The general formula for the mayenite supergroup issimplified to X12T14O32"x(OH)3x[W6"3x], with thetwo tetrahedral sites T1 and T2 considered as a singleunit. Distinctions between the mineral species are basedon charge at the W site and on cations at the two T sitesconsidered together. We distinguish two groups in themayenite supergroup, they differ in charge at theW site:the mayenite group (W¼ –2) and the wadalite group (W¼ –6).

" Minerals in the mayenite supergroup are isostructuralwith the synthetic phase mayenite (Ca12Al14O32[&5O]).

" Re-examination of the holotype mayenite (Eifel,Germany) showed that it has the end-member formulaCa12Al14O32[&4Cl2], and is thus renamed as chlor-mayenite, whereas mayenite is retained as a group name.

" Brearleyite, also given as Ca12Al14O32Cl2 orCa12Al14O32[&4Cl2], is thus identical to chlormaye-nite. The name mayenite has priority, and thus thename brearleyite is discredited in favour of the namederived from mayenite, chlormayenite.

" Kyuygenite (Ca12Al14O32[(H2O)4Cl2]) is renamed aschlorkyuygenite.

Table 4. Possible end-members and known synthetic phases

Mayenite supergroup Simplifiedformula X12 T14 O32–x OH/F3x W6-2x Maximum of end-member Synth.

Mayenite group (Wcharge ¼ –2, x ¼ 0)Ca12Al14O32[&5O] Ca12Al14O33 Ca12 Al14 O32 &5O ?? YesCa12Al14O32[&4(OH)2] Ca12Al14O32(OH)2 Ca12 Al14 O32 &4(OH)2 &5% in chlor- and

fluormayeniteYes

Ca12Fe3þ14O32[&4(OH)2] Ca12Fe3þ

14O32(OH)2 Ca12 Fe3þ14 O32 &4(OH)2 , 1% in chlormayenite No

Ca12Fe3þ14O32[&4Cl2] Ca12Fe3þ

14O32Cl2 Ca12 Fe3þ14 O32 &4Cl2 10% in chlormayenite No

Ca12Fe3þ14O32[&4F2] Ca12Fe3þ

14O32F2 Ca12 Fe3þ14 O32 &4F2 2% in fluormayenite No

Ca12Fe3þ14O32[(H2O)4Cl2] Ca12 Fe3þ

14 O32 (H2O)4Cl2 , 2% in chlorkyuygenite NoCa12Fe3þ

14O32[(H2O)4F2] Ca12 Fe3þ14 O32 (H2O)4F2 ,2% in fluorkyuygenite No

Ca12Fe3þ14O32[(H2O)4(OH)2] Ca12 Fe3þ

14 O32 (H2O)4(OH)2 ,2% in chlorkyuygenite NoCa12Al14O32[(H2O)4(OH)2] Ca12 Al14 O32 (H2O)4(OH)2 &14% in fluorkyuygenite NoSr12Al14O32[&4Cl2] Sr12Al14O32Cl2 Sr12 Al14 O32 &5Cl2 ,1% in chlormayenite Yes

Wadalite group (Wcharge ¼ –6, x ¼ 0)Ca12Fe3þ

10Si4O32[F6] Ca12Fe3þ10Si4O32F6 Ca12 Fe3þ

10Si4 O32 F6 ,2% in eltyubyuite NoCa12Mg5Si9O32[Cl6]* Ca12Mg5Si9O32Cl6 Ca12 Si9Mg5 O32 Cl6 & 40% in wadalite Yes{Y4Ca8}Al14O32[Cl6] Y4Ca8Al14O32Cl6 Y4Ca8 Al14 O32 Cl6 &10 % in chlorkyuygenite No

Ungrouped (Wcharge ¼ 0, x ¼ 2)Ca12Al14O30(OH)6&6 Ca12Al14O30(OH)6 Ca12 Al14 O30 (OH)6 &6 & 40% in chlormayenite NoCa12Al14O30F6&6 Ca12Al14O30F6 Ca12 Al14 O30 F6 &6 &3% in fluormayenite??? No?????&Ca12Fe3þ

10Si4O30F10** Ca12 Fe3þ

10Si4 O30F10 anthropogenic phase No

*synthetic phase Ca12Al2Mg4Si8Cl6 (Gfeller, unpublished data)** anthropogenic phase (Sharygin, 2014)


eschweizerbart_xxx

" Re-examination of mayenite from the Hatrurim for-mation, Israel revealed the presence of fluorine analo-gues of chlormayenite, fluormayenite (Ca12Al14O32

[&4F2]) and of chlorkyuygenite, fluorkyuygenite(Ca12Al14O32[(H2O)4F2]), respectively.

" The mayenite group includes chlormayenite (Ca12Al14

O32[&4Cl2]), fluormayenite (Ca12Al14O32[&4F2]),chlorkyuygenite (Ca12Al14O32[(H2O)4Cl2]), and fluor-kyuygenite (Ca12Al14O32[(H2O)4F2]).

" The wadalite group includes wadalite (Ca12Al10Si4O32

[Cl6]) and eltyubyuite (Ca12Fe3þ10Si4O32[Cl6]).

" Analysis of possible isomorphic substitutions and dataon synthetic and anthropogenic phases suggests thepossibility of three additional new mineral species.

Acknowledgements: The holotype specimen No. M5026/86 and the type specimen No. 120045 of mayenite andbrownmillerite were kindly provided by the MineralMuseum, University of Cologne, Germany and by theNational Museum of Natural History, Washington, D.C.,USA, respectively. Ed Grew is thanked for comments ondrafts of this paper. The authors thank S. Mills and ananonymous reviewer for their careful revision thatimproved the early version of the manuscript.Investigations were partially supported by the NationalSciences Centre (NCN) of Poland by decision no. DEC-2012/05/B/ST10/00514 (E.G. and I.G.).

References

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Received 7 July 2014Modified version received 2 October 2014Accepted 5 October 2014


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mayenite supergroup, part i: recommended nomenclature

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