The information given here is provided by the IMA Commission on New Minerals, Nomenclature and Classification for comparative purposes and as a service to mineralogists working on new species.
Each mineral is described in the following format:
Mineral name, if the authors agree on its release prior to the full description appearing in press
Chemical formula
Type locality
Full authorship of proposal
E-mail address of corresponding author
Relationship to other minerals
Crystal system, Space group; Structure determined, yes or no
Unit-cell parameters
Strongest lines in the powder X-ray diffraction pattern
Type specimen repository and specimen number
Citation details for the mineral prior to publication of full description
Citation details concern the fact that this information will be published in the Mineralogical Magazine on a routine basis, as well as being added month by month to the Commission's web site.
It is still a requirement for the authors to publish a full description of the new mineral.
NO OTHER INFORMATION WILL BE RELEASED BY THE COMMISSION
NEW MINERAL PROPOSALS APPROVED IN FEBRUARY 2018
IMA No. 2017-094
Ammoniolasalite
[(NH4)2Mg2(H2O)20]·[V10O28]
Burro mine, Slick Rock district, San Miguel Co., Colorado, USA (38°2'42”N, 108°53'23”W)
Anthony R. Kampf*, Barbara P. Nash, Paul M. Adams, Joe Marty and John M. Hughes
*E-mail: [email protected]
The ammonium analogue of lasalite
Monoclinic: C2/c; structure determined
a = 24.478(3), b = 10.9413(4), c = 17.551(1) Å, β = 119.257(7)°
10.64(24), 9.43(100), 8.57(21), 7.62(26), 6.80(32), 2.891(13), 2.725(23), 2.125(13)
Cotype material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, California, USA, catalogue numbers 67477, 67478, 67479, 67480 and 67481
How to cite: Kampf, A.R., Nash, B.P., Adams, P.M., Marty, J. and Hughes, J.M. (2018) Ammoniolasalite, IMA 2017-094. CNMNC Newsletter No. 42, April 2018, page 446; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-099
Ferrierite-NH4
(NH4,Mg0.5)5(Al5Si31O72)·22H2O
Libous lignite quarry, near Chomutov, Ústí Region, Bohemia, Czech Republic
Nikita V. Chukanov*, Igor V. Pekov, Dmitriy I. Belakovskiy and Sergey N. Britvin
*E-mail: [email protected]
Zeolite supergroup
Orthorhombic: Immm
a = 19.10(1), b = 14.15(1), c = 7.489(3) Å
9.52(97), 6.95(28), 6.60(19), 3.988(61), 3.784(19), 3.547(73), 3.482(100), 3.143(37)
Type material is deposited in the collections of the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, registration number 5120/1
How to cite: Chukanov, N.V., Pekov, I.V., Belakovskiy, D.I. and Britvin, S.N. (2018) Ferrierite-NH4, IMA 2017-099. CNMNC Newsletter No. 42, April 2018, page 446; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-100
Nollmotzite
Mg[U5+(U6+O2)2O4F3]·4H2O
Clara mine, Black Forest Mountains, Baden-Württemberg, Germany (48°22'59”N, 8°14'47”E)
Jakub Plášil*, Anthony R. Kampf, Radek Škoda and Jiří Čejka
*E-mail: [email protected]
New structure type
Monoclinic: Cm; structure determined
a = 7.1122(4), b = 11.7733(7), c = 8.2075(4) Å, β = 98.623(4)°
8.10(100), 4.060(31), 3.518(30), 3.420(54), 3.237(22), 3.083(26), 2.710(17), 2.015(32)
Cotype material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, California, USA, catalogue numbers 66647, 66648 and 66649
How to cite: Plášil, J., Kampf, A.R., Škoda, R. and Čejka, J. (2018) Nollmotzite, IMA 2017-100. CNMNC Newsletter No. 42, April 2018, page 446; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-101
Dellagiustaite
V2+Al2O4
Sierra de Comechingones, San Luis, Argentina
Fernando Cámara*, Renato Pagano, Adriana Pagano and Luca Bindi
*E-mail: [email protected]
Spinel supergroup
Cubic: Fd 
$\overline 3 $ m; structure determined
a = 8.1950(1) Å
2.469(19), 2.047(58), 1.576(38), 1.447(100), 1.182(27), 1.023(87), 0.915(21), 0.836(35)
Type material is deposited in the mineralogical collections of the Museo delle Collezioni di Mineralogia, Gemmologia, Petrologia e Giacimentologia, Dipartimento di Scienze della Terra “A. Desio”, Università di Milano, catalogue number MCMGPG-H2017-001
How to cite: Cámara, F., Pagano, R., Pagano, A. and Bindi, L. (2018) Dellagiustaite, IMA 2017-101. CNMNC Newsletter No. 42, April 2018, page 446; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-102
Potassic-richterite
K(NaCa)Mg5Si8O22(OH)2
Stora Pajsberg mine, Filipstad, Värmland, Sweden (59°47.04'N, 14°19.03'E); or Harstigen mine, Filipstad, Värmland, Sweden (59°47.10'N, 14°18.84'E)
Dan Holtstam*, Fernando Cámara, Henrik Skogby and Andreas Karlsson
*E-mail: [email protected]
Amphibole supergroup
Monoclinic: C2/m; structure determined
a = 9.9977(3), b = 18.0409(4), c = 5.2794(2) Å, β = 104.465(4)°
8.55(36), 3.303(56), 3.181(100), 2.847(50), 2.714(37), 2.173(25), 1.668(27), 1.456(32)
Type material is deposited in the mineralogical collections of the Department of Geosciences, Swedish Museum of Natural History, Box 50007, SE-10405 Stockholm, Sweden, collection number NRM19311387
How to cite: Holtstam, D., Cámara, F., Skogby, H. and Karlsson, A. (2018) Potassic-richterite, IMA 2017-102. CNMNC Newsletter No. 42, April 2018, page 447; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-103
Magnesiofluckite
CaMg(AsO3OH)2(H2O)2
Torrecillas mine, Salar Grande, Iquique Province, Tarapacá Region, Chile (20°58'13”S, 70°8'17”W)
Anthony R. Kampf*, Barbara P. Nash, Maurizio Dini and Arturo A. Molina Donoso
*E-mail: [email protected]
The Mg analogue of fluckite
Triclinic: P 
$\overline 1 $; structure determined
a = 8.4143(6), b = 7.5321(5), c = 6.8917(4) Å, α = 82.477(6), β = 97.682(6), γ = 95.379(6)°
7.46(78), 4.92(43), 4.191(45), 3.511(100), 3.248(81), 2.953(62), 2.796(51), 2.679(75)
Type material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, California, USA, catalogue number 67257
How to cite: Kampf, A.R., Nash, B.P., Dini, M. and Molina Donoso, A.A. (2018) Magnesiofluckite, IMA 2017-103. CNMNC Newsletter No. 42, April 2018, page 447; Mineralogical Magazine, 82, 445–451.
NEW MINERAL PROPOSALS APPROVED IN MARCH 2018
IMA No. 2017-084
Lasnierite
(Ca,Sr)(Mg,Fe2+)2Al(P[O,F]4)3
Mount Ibity, ca. 30 km NNE of Soavina, Ambatofinandrahana district, and 10 km SW of Manandona, Antsirabé 2 District, Vakinankaratra Region, Antananarivo Province, Madagascar
Benjamin Rondeau*, Bertrand Devouard, Damien Jacob, Pascal Roussel, Nicolas Stéphant, Constance Boulet, Valentin Mollé, Marianna Corre, Emmanuel Fritsch, Cristiano Ferraris and Gian Carlo Parodi
*E-mail: [email protected]
New structure type
Orthorhombic: Pbcn; structure determined
a = 6.2771(3), b = 17.684(3), c = 8.1631(4) Å
4.421(83), 3.802(63), 3.706(100), 3.305(99), 2.890(90), 2.781(69), 2.772(67), 2.601(97)
Type material is deposited in the mineralogical collections of the Muséum National d'Histoire Naturelle (MNHN), 61 rue Buffon, 75005 Paris, France, registration number MNHN 217.001
How to cite: Rondeau, B., Devouard, B., Jacob, D., Roussel, P., Stéphant, N., Boulet, C., Mollé, V., Corre, M., Fritsch, E., Ferraris, C. and Parodi, G.C. (2018) Lasnierite, IMA 2017-084. CNMNC Newsletter No. 42, April 2018, page 447; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-104
Vandermeerscheite
K2[(UO2)2V2O8]·2H2O
Schellkopf, Brenk, Eifel, Rhineland-Palatinate, Germany
Jakub Plášil*, Anthony R. Kampf, Radek Škoda and Jiří Čejka
*E-mail: [email protected]
Chemically close to carnotite
Monoclinic: P21/n; structure determined
a = 8.292(2), b = 8.251(3), c = 10.188(3) Å, β = 110.84(4)°
7.49(100), 4.147(22), 3.738(32), 3.616(20), 3.254(31), 3.132(21), 2.989(41), 2.091(13)
Cotype material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, California, USA, catalogue numbers 67260, 67261 and 67262
How to cite: Plášil, J., Kampf, A.R., Škoda, R. and Čejka, J. (2018) Vandermeerscheite, IMA 2017-104. CNMNC Newsletter No. 42, April 2018, page 447; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-105
Khrenovite
Na3Fe3+2(AsO4)3
Arsenatnaya fumarole, Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka peninsula, Far-Eastern Region, Russia (55°41'N, 160°14'E, 1200 m asl)
Igor V. Pekov*, Natalia N. Koshlyakova, Dmitry I. Belakovskiy, Marina F. Vigasina, Natalia V. Zubkova, Atali A. Agakhanov, Sergey N. Britvin, Evgeny G. Sidorov and Dmitry Y. Pushcharovsky
*E-mail: [email protected]
Alluaudite group
Monoclinic: C2/c; structure determined
a = 12.2394(7), b = 12.7967(5), c = 6.6589(4) Å, β = 112.953 (7)°
6.40(48), 5.639(48), 3.582(41), 3.198(62), 2.939(33), 2.824(60), 2.785(100), 2.612(33)
Type material is deposited in the collections of the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, registration number 5028/1
How to cite: Pekov, I.V., Koshlyakova, N.N., Belakovskiy, D.I., Vigasina, M.F., Zubkova, N.V., Agakhanov, A.A., Britvin, S.N., Sidorov, E.G. and Pushcharovsky, D.Y. (2018) Khrenovite, IMA 2017-105. CNMNC Newsletter No. 42, April 2018, page 448; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-106
Chinchorroite
Na2Mg5(As2O7)2(AsO3OH)2(H2O)10
Torrecillas mine, Salar Grande, Iquique Province, Tarapacá Region, Chile (20°58'13”S, 70°8'17”W)
Anthony R. Kampf*, Barbara P. Nash, Maurizio Dini and Arturo A. Molina Donoso
*E-mail: [email protected]
New structure type
Triclinic: P 
$\overline 1 $; structure determined
a = 8.7777(2), b = 8.8570(3), c = 9.7981(7) Å, α = 91.097(6), β = 110.544(8), γ = 103.167(7)°
9.10(100), 8.63(54), 5.25(32), 4.034(49), 3.521(35), 3.036(53), 2.811(42), 2.568(36)
Type material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, California, USA, catalogue number 67257
How to cite: Kampf, A.R., Nash, B.P., Dini, M. and Molina Donoso, A.A. (2018) Chinchorroite, IMA 2017-106. CNMNC Newsletter No. 42, April 2018, page 448; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-107
Nöggerathite-(Ce)
(Ce,Ca)2Zr2(Nb,Ti)(Ti,Nb)2Fe2+O14
In den Dellen (Zieglowski) pumice quarry, 1.5 km NE of Mendig, Laach Lake (Laacher See) volcano, Eifel region, Rhineland-Palatinate, Germany
Nikita V. Chukanov*, Natalia V. Zubkova, Sergey N. Britvin, Igor V. Pekov, Marina F. Vigasina, Christof Schäfer, Bernd Ternes, Willi Schüller, Vera N. Ermolaeva and Dmitry Y. Pushcharovsky
*E-mail: [email protected]
Isostructural with zirconolite
Orthorhombic: Cmca; structure determined
a = 7.2985(3), b = 14.1454(4), c = 10.1607(4) Å
3.689(10), 2.963(91), 2.903(100), 2.540(39), 1.823(15), 1.796(51), 1.543(20), 1.519(16)
Type material is deposited in the collections of the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, registration number 5123/1
How to cite: Chukanov, N.V., Zubkova, N.V., Britvin, S.N., Pekov, I.V., Vigasina, M.F., Schäfer, C., Ternes, B., Schüller, W., Ermolaeva, V.N. and Pushcharovsky, D.Y. (2018) Nöggerathite-(Ce), IMA 2017-107. CNMNC Newsletter No. 42, April 2018, page 448; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-108
Rhabdoborite-(V)
Mg12(V5+,Mo6+,W6+)1.5O6{[BO3]6–x[(P,As)O4]xF2–x} (x < 1)
Arsenatnaya fumarole, Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka peninsula, Far-Eastern Region, Russia (55°41'N, 160°14'E, 1200 m asl)
Igor V. Pekov*, Natalia V. Zubkova, Natalia N. Koshlyakova, Dmitry I. Belakovskiy, Marina F. Vigasina, Atali A. Agakhanov, Sergey N. Britvin, Evgeny G. Sidorov and Dmitry Y. Pushcharovsky
*E-mail: [email protected]
Isostructural with rhabdoborite-(W) (IMA No. 2017-109)
Hexagonal: P63; structure determined
a = 10.6314(4), c = 4.5661(2) Å
9.17(100), 5.301(44), 3.472(76), 2.763(64), 2.547(61), 2.226(79), 1.701(63), 1.474(31)
Type material is deposited in the collections of the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, registration number 5125/1
How to cite: Pekov, I.V., Zubkova, N.V., Koshlyakova, N.N., Belakovskiy, D.I., Vigasina, M.F., Agakhanov, A.A., Britvin, S.N., Sidorov, E.G. and Pushcharovsky, D.Y. (2018) Rhabdoborite-(V), IMA 2017-108. CNMNC Newsletter No. 42, April 2018, page 448; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-109
Rhabdoborite-(W)
Mg12(W6+,V5+)1.5O6{[BO3]6–x[(P,As)O4]xF2–x} (x < 1)
Arsenatnaya fumarole, Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka peninsula, Far-Eastern Region, Russia (55°41'N, 160°14'E, 1200 m asl)
Igor V. Pekov*, Natalia V. Zubkova, Natalia N. Koshlyakova, Dmitry I. Belakovskiy, Marina F. Vigasina, Atali A. Agakhanov, Sergey N. Britvin, Evgeny G. Sidorov and Dmitry Y. Pushcharovsky
*E-mail: [email protected]
Isostructural with rhabdoborite-(V) (IMA No. 2017-108)
Hexagonal: P63; structure determined
a = 10.6366(5), c = 4.5701(3) Å
9.18(100), 5.304(38), 4.595(25), 3.479(61), 2.766(29), 2.550(30), 2.228(35), 1.703(25)
Type material is deposited in the collections of the the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, registration number 5126/1
How to cite: Pekov, I.V., Zubkova, N.V., Koshlyakova, N.N., Belakovskiy, D.I., Vigasina, M.F., Agakhanov, A.A., Britvin, S.N., Sidorov, E.G. and Pushcharovsky, D.Y. (2018) Rhabdoborite-(W), IMA 2017-109. CNMNC Newsletter No. 42, April 2018, page 449; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-110
Pararaisaite
CuMg[Te6+O4(OH)2]·6H2O
North Star mine, Mammoth, Tintic district, Juab Co., Utah, USA (39°55'14”N, 112°6'28”W)
Anthony R. Kampf*, Robert M. Housley and George R. Rossman
*E-mail: [email protected]
A dimorph of raisaite
Monoclinic: P21/c; structure determined
a = 9.6838(5), b = 5.7517(2), c = 17.634(1) Å, β = 90.553(6)°
8.77(100), 4.824(71), 4.392(43), 4.248(85), 2.733(39), 2.419(50), 1.893(48), 1.753(29)
Type material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, California, USA, catalogue number 67272
How to cite: Kampf, A.R., Housley, R.M. and Rossman, G.R. (2018) Pararaisaite, IMA 2017-110. CNMNC Newsletter No. 42, April 2018, page 449; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-111
Thalhammerite
Pd9Ag2Bi2S4
Komsomolsky mine, Talnakh deposit, Noril'sk region, Russia (69°30'20”N, 88°27'17”E)
Anna Vymazalová*, František Laufek, Sergei F. Sluzhenikin, Vladimir V. Kozlov, Chris J. Stanley, Jakub Plášil, Federica Zaccarini, Giorgio Garuti and Ronald Bakker
*E-mail: [email protected]
Known synthetic analogue
Tetragonal: I4/mmm; structure determined
a = 8.0266(2), c = 9.1531(2) Å
3.343(24), 2.839(46), 2.412(100), 2.324(61), 2.287(48), 2.220(29), 2.007(40), 1.508(30)
Type material is deposited in the mineralogical collections of the Natural History Museum, Cromwell Road, SW7 5BD London, UK, catalogue No. BM2017,16
How to cite: Vymazalová, A., Laufek, F., Sluzhenikin, S.F., Kozlov, V.V., Stanley, C.J., Plášil, J., Zaccarini, F., Garuti, G. and Bakker, R. (2018) Thalhammerite, IMA 2017-111. CNMNC Newsletter No. 42, April 2018, page 449; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-112
Mitrofanovite
Pt3Te4
East Chuarvy, Fedorovo-Pana intrusion, Kola Peninsula, Russia (67°24'30”N, 36°03'00”E)
Viktor V. Subbotin, Anna Vymazalová*, František Laufek, Yevgeny E. Savchenko, Chris J. Stanley, Dmitriy A. Gabov and Jakub Plášil
*E-mail: [email protected]
Structurally and chemically related to moncheite
Trigonal: R 
$\overline 3 $ m; structure determined
a = 3.9875(1), c = 35.362(7) Å
11.79(23), 5.891(100), 3.928(11), 2.851(26), 2.137(16), 2.039(18), 1.574(24), 1.310(21)
Type material is deposited in the collections of the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, registration number 5141/1
How to cite: Subbotin, V.V., Vymazalová, A., Laufek, F., Savchenko, Y.E., Stanley, C.J., Gabov, D.A. and Plášil, J. (2018) Mitrofanovite, IMA 2017-112. CNMNC Newsletter No. 42, April 2018, page 450; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-113
Jahnsite-(MnMnZn)
Mn2+Mn2+Zn2Fe3+2(PO4)4(OH)2·8H2O
Herdade dos Pendões mine, ca. 5 km N of the village of Odemira, Beja district, Portugal (37°38'33”N, 8°37'52”W)
Anthony R. Kampf*, Pedro Alves, Anatoly Kasatkin and Radek Škoda
*E-mail: [email protected]
Jahnsite group
Monoclinic: P2/a
a = 15.222(6), b = 7.187(6), c = 10.028(5) Å, β = 111.746(16)°
9.25(63), 5.00(40), 4.648(33), 3.509(41), 2.842(100), 1.998(37), 1.951(30), 1.585(33)
Type material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, California, USA, catalogue number 67277
How to cite: Kampf, A.R., Alves, P., Kasatkin, A. and Škoda, R. (2018) Jahnsite-(MnMnZn), IMA 2017-113. CNMNC Newsletter No. 42, April 2018, page 450; Mineralogical Magazine, 82, 445–451.
IMA No. 2017-078a
Kaitianite
Ti3+2Ti4+O5
Allende CV3 meteorite, fell at Pueblito de Allende, Chihuahua, Mexico
Ma, C.*
*E-mail: [email protected]
The Ti analogue of oxyvanite
Monoclinic: C2/c
a = 10.115, b = 5.074, c = 7.182 Å, β = 112.0°
4.689(53), 3.377(75), 2.931(73), 2.662(100), 2.466(59), 1.737(66), 1.671(67), 1.451(52)
Type material is deposited in the mineralogical collections of the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA, section UNSM 3510-5
How to cite: Ma, C. (2017) Kaitianite, IMA 2017-078. CNMNC Newsletter No. 42, April 2018, page 450; Mineralogical Magazine, 82, 445–451.
NOMENCLATURE PROPOSALS APPROVED IN MARCH 2018
IMA 17-H: Spinel supergroup
Proposal 17-H on the classification of the spinel supergroup is accepted. The fifty-three minerals of the spinel supergroup are divided into three groups on the basis of dominant X anion: O2– (oxyspinel), S2– (thiospinel), and Se2– (seleniospinel). Each group is divided into subgroups according to the dominant valence and then the dominant constituent (or heterovalent-pair of constituents) represented by the letter B in the formula AB 2X 4. The oxyspinel group can be divided into spinel subgroup 2-3 (A 2+B 3+2O4) and ulvöspinel subgroup 4-2 (A 4+B 2+2O4), thiospinel group into carrollite subgroup 1-3.5 (A 1+B 3.5+2S4) and linnaeite subgroup 2-3 (A 2+B 3+2S4), and the selenospinel group into bornhardtite subgroup 2-3 (A 2+B 3+2Se4) and tyrrellite. Once the subgroup is established by the valence of B and the dominant B-cation, then the mineral species is identified by the dominant A-cation. There are thirty species in the oxyspinel group, twenty in the thiospinel group and three in the seleniospinel group.
IMA 17-I: Revised end-member formula for flurlite
Proposal 17-I is accepted. A re-evaluation of the site occupancies in flurlite, using BVS calculations, resulted in a change in the dominant cation in the M1 site from Mn2+ to Zn. Consequently, the end-member formula for flurlite becomes [5]Zn [6]Zn3[6]Fe3+(PO4)3(OH)2(H2O)7·2H2O.
IMA 18-A: Redefinition of eztlite
Proposal 18-A is accepted, and the formula for eztlite is redefined, according to new analytical results. The previously accepted formula, published by Sidney Williams in 1982, was Fe3+6Pb2+2(Te4+O3)3(Te6+O6)(OH)10·nH2O, with n ≈ 8. This formula is now redefined to Pb2+2Fe3+3(Te4+O3)3(SO4)O2Cl.
Nepheline - revised chemical formula
In the IMA List of Minerals the ideal chemical formulae of kalsilite and nepheline are given as KAlSiO4 and NaAlSiO4, respectively. Whereas the formula of kalsilite is correct, nepheline must contain some amount of potassium substituting for sodium. Both kalsilite and nepheline are hexagonal, space group P63. In kalsilite, which has a smaller unit cell, all cavities which host alkali cations have a hexagonal outline and are occupied by potassium; in nepheline, due to the doubling of the a parameter, there are 3 cavities with oval outline and 1 cavity with hexagonal outline: the former are occupied by sodium, the latter by potassium. Accordingly, the chemical formula of nepheline should be Na3K(Al4Si4O16). All known chemical analyses of nepheline, including those of nepheline from the type locality (Monte Somma – Vesuvius area, Italy) match the above formula. Therefore potassium is an essential constituent of nepheline and it should appear in the chemical formula of the mineral. This is an executive decision taken by the officers of the IMA CNMNC.
