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MINERAL CLASSIFICATION / SYSTEMATIK der MINERALE

           based on E.H. Nickel & M.C. Nichols (2009), H. Strunz & E.H. Nickel (2001),
           revised by Thomas Witzke (2023)



5. CARBONATES
(Carbonates, Nitrates)


5.D: Carbonates with additional anions, with water


5.DA. With cations only in tetrahedral coordination
 
no example known
 


 
5.DB. With cations in tetrahedral + other coordination
 
5.DB.005. Niveolanite
 
Niveolanite NaBe(CO3)(OH)·2H2O tetr., P4/mcc FOTO IMA 2007-032

Niveolanite: The structure contains infinite chains of BeO2(OH)2 tetrahedra, linked via common OH groups. The two other vertices of each Be tetrahedron are shared with (CO3) groups. Na cations occupy seven-fold polyhedra NaO6(H2O) forming columns. Chains of Be tetrahedra and columns of Na polyhedra are aligned along the c axis. H2O molecules are located in channels formed by the chains and columns (Pekov et al., 2008, Can. Min. 46, 1343-1354).


 
5.DB.010. Šlikite
 
Šlikite Zn2Mg(CO3)2(OH)2·4H2O tric., P1 IMA 2018-120

Šlikite: The structure contains heteropolyhedral layers of composition [Zn4Mg(CO3)4(OH)4]2-, parallel to {001}. Within the layers, [110] chains of corner-connected ZnO2(OH)2 tetrahedra share corners with Mg-centred octahedra. Tetrahedra and octahedra are connected via CO3 groups. The interlayer between these layers is composed of H-bonded [Mg(H2O)6]2+ octahedra and H2O (Sejkora et al., 2019, Eur. J. Min. 31, 1047-1054).



 
 
5.DC. With cations only in octahedral coordination
 
5.DC.005. Scarbroite group
 
Scarbroite Al5(CO3)(OH)13·5H2O tric., P1 or P1 G
Hydroscarbroite Al14(CO3)3(OH)36·nH2O Q

Scarbroite: probably structurally closely related to Gibbsite and Hydrotalcite-group minerals, with an aluminiumhydroxide layer of corner-sharing AlO6-octahedra and a carbonate-water interlayer. Not all Al positions are occupied (Brindley, 1980, Min. Mag. 43, 615-618).
Hydroscarbroite needs a re-study. As it dehydrates to Scarbroite (Duffin & Goodyear, 1960, Min. Mag. 32, 353-362), the formula should be simply a higher hydrate.
With better structural data, the minerals could be placed in Oxides/Hydroxides 4.FM. as the Hydrotalcite group minerals. Felsöbanyaite and Hydrobasaluminite are probably closely related minerals with sulfate in the interlayer.


 
5.DC.010. Artinite group
 
Artinite Mg2(CO3)(OH)2·3H2O mon., C2/m G
Chlorartinite Mg2(CO3)(OH)Cl·3H2O trig., R3c IMA 1996-005

Artinite: Double-chains of edge-sharing MgO(OH)2(H2O)3 octahedra. The chains are connected via CO3 groups (Jagodzinski, 1965, Tscherm. Min. Petr. Mitt. 10, 297).


 
5.DC.015. Hydromagnesite group
 
Hydromagnesite Mg5(CO3)4(OH)2·4H2O mon., P21/c FOTO G
Widgiemoolthalite Ni5(CO3)4(OH)2·5H2O mon., P21/c (?) FOTO IMA 1992-006
Dypingite Mg5(CO3)4(OH)2·5H2O mon. FOTO IMA 1970-011
Giorgiosite Mg5(CO3)4(OH)2·5H2O mon. (?) Q

Hydromagnesite: Three-dimensional framework of MgO6 octahedra and carbonate groups (Akao et al., 1970, Acta Cryst. B30, 2670-2672).
Widgiemoolthalite: structure analysis not possible, from the powder data very probably isostructural with Hydromagnesite, with some disorder and possible superstructure in b direction (Nickel at al., 1993, Am. Min. 78, 819-821).
The structure of Dypingite is unknown, but probably similar to Hydromagnesite.
Giorgiosite needs further study, tentatively placed here.


 
5.DC.020. Kambaldaite
 
Kambaldaite NaNi4(CO3)3(OH)3·3H2O hex., P63 FOTO IMA 1982-098

Kambaldaite: distorted NiO6 octahedra linked in a three-dimensional array with bridging carbonate and hydroxyl groups. Na(H2O)6 octahedra occupy columnar tunnels in the structure (Engelhardt et al., 1985, Am. Min. 70, 423-427).


 
5.DC.025. Otwayite
 
Otwayite Ni2(CO3)(OH)2·H2O mon., P21/c G

Otwayite: structure not determined, octahedral coordination of Ni assumed, tentatively placed here.


 
5.DC.030. Zaratite
 
Zaratite Ni3(CO3)1+x(OH)4-2x·nH2O, x = 0.3-2, n < 3.5 amorphous Q

Zaratite: formula usually given as Ni3(CO3)(OH)4·4H2O. Re-investigation of type material and other samples showed a more variable composition represented by the formula given above. Real Zaratite is amorphous and my represent more than one species, several samples labeled as Zaratite are mixtures or other Ni minerals (Garcia-Guinea et al., 2013, Eur. J. Min. 25, 995-1004).
Tentatively placed here, octahedral coordination of Ni is assumed.


 
5.DC.035. Marklite
 
Marklite Cu5(CO3)2(OH)6·6H2O mon., P21/c IMA 2015-101

Marklite: infinite sheets of edge-sharing distorted Cu-octahedra, of the composition {Cu2+4O2(OH)6} parallel to (100). Adjacent sheets are linked through the interstitial {Cu2+(H2O)2(CO3)2} complex, which consists of a distorted Cu2+ tetragonal bipyramid with two H2O and four oxygen from two carbonate groups (Plášil, 2016, Int. Sci. Symposium Jáchymov, 75-78).


 
5.DC.040. Indigirite
 
Indigirite Mg2Al2(CO3)4(OH)2·15H2O mon. (?) IMA 1971-012

Indigirite: structure not determined, tentatively placed here.



 
 
5.DD. With cations in octahedral + other coordination
 
5.DD.005. Callaghanite
 
Callaghanite Cu2Mg2(CO3)(OH)6·2H2O mon., C2/c FOTO G

Callaghanite: Mg in octahedral coordination, Cu in 5-fold, tetragonal-pyramidal coordination.


 
5.DD.010. Alumohydrocalcite group
 
Alumohydrocalcite CaAl2(CO3)2(OH)4·3H2O tric. FOTO A
Grguricite CaCr2(CO3)2(OH)4·3H2O tric., P1 IMA 2019-123

Alumohydrocalcite and Grguricite: trivalent cations (Al and Cr) in octahedral coordination, Ca in 7-fold coordination (pentagonal bipyramids).


 
5.DD.015. Dundasite group
 
Kochsándorite CaAl2(CO3)2(OH)4·H2O orth., Pnma FOTO IMA 2004-037
Strontiodresserite SrAl2(CO3)2(OH)4·H2O orth., Pnma IMA 1977-005
Dundasite PbAl2(CO3)2(OH)4·H2O orth., Pnma G
Petterdite PbCr2(CO3)2(OH)4·H2O orth., Pnma FOTO IMA 1999-034
Dresserite BaAl2(CO3)2(OH)4·1.5H2O orth. FOTO IMA 1968-027

Dundasite: Al in octahedral coordination, Pb in 9-fold coordination (Cocco et al., 1972, Min. Mag. 38, 564-569).
Strontiodresserite is isostructural (Whitfield et al., 2010, Powder Diffraction Journal 25, 322-328).
Space group of Dundasite and Petterdite usually given in the non-standard setting Pbnm.
Space group of Dresserite possibly Pbmm, Pb21m or Pbm2.


 
5.DD.020. Hydrodresserite
 
Hydrodresserite BaAl2(CO3)2(OH)4·3H2O tric., P1 IMA 1976-036

Hydrodresserite: Al in distorted octahedral coordination, 4 with oxygen from hydroxyl groups in a square and 2 oxygen from carbonate groups. Ba in 9-fold coordination with oxygen from water, carbonate groups and hydroxyl (Szymanski, 1982, Can. Min. 20, 253-262.


 
5.DD.025. Para-alumohydrocalcite
 
Para-alumohydrocalcite CaAl2(CO3)2(OH)4·6H2O mon. or tric. IMA 1976-027

Para-alumohydrocalcite: structure not determined, tentatively placed here.


 
5.DD.030. Montroyalite
 
Montroyalite Sr4Al8(CO3)3(OH)26·10H2O tric. IMA 1985-001a

Montroyalite: structure not determined, tentatively placed here.


 
5.DD.030. Sergeevite
 
Sergeevite Ca2Mg11(HCO3)4(CO3)9(OH)4·6H2O trig. IMA 1979-038

Sergeevite: structure not determined, tentatively placed here.


 
5.DD.035. Lusernaite
 
Lusernaite-(Y) Y4Al(CO3)2(OH)10F·6H2O orth., Pnma IMA 2011-108

Lusernaite-(Y): Al in octahedral coordination, Y on two different positions in 8-fold coordination (Biagioni et al., 2013, Am. Min. 98, 1322-1329).


 
5.DD.040. Decrespignyite
 
Decrespignyite-(Y) Y4Cu(CO3)4Cl(OH)5·3H2O mon. FOTO IMA 2001-027

Decrespignyite-(Y): structure not determined, probably a layer structure. Discussed is a structure of two layer types, one type containing carbonate groups and Y in 9-fold coordination, and a second type containing Cu in octahedral coordination (Wallwork et al., 2002, Min Mag 66, 181-188).



 
 
5.DE. With cations in other coordination
 
5.DE.005. Ancylite group
 
Calcioancylite-(La) (CaLa)(CO3)2(OH)(H2O) orth., Pmcn IMA 2021-090
Calcioancylite-(Ce) (CaCe)(CO3)2(OH)(H2O) orth., Pmcn FOTO A
Calcioancylite-(Nd) (CaNd)(CO3)2(OH)(H2O) mon., Pm IMA 1989-008
Ancylite-(La) (SrLa)(CO3)2(OH)(H2O) orth., Pmcn IMA 1995-053
Ancylite-(Ce) (SrCe)(CO3)2(OH)(H2O) orth., Pmcn FOTO A
Gysinite-(La) (PbLa)(CO3)2(OH)(H2O) orth., Pmcn IMA 2022-008
Gysinite-(Ce) (PbCe)(CO3)2(OH)(H2O) orth., Pmcn IMA 2023-035
Gysinite-(Nd) (PbNd)(CO3)2(OH)(H2O) orth., Pmcn IMA 1981-046
Kozoite-(La) La(CO3)(OH) orth., Pmcn IMA 2002-054
Kozoite-(Nd) Nd(CO3)(OH) orth., Pmcn IMA 1998-063

The general formula of the Ancylite group minerals can be given as (REE3+2-xMe2+x)(CO3)2(OH)2-x(H2O)x with x = 0 - 1.
REE and Me2+ occupy the same crystallographical site, the cations are in 8-fold coordination with oxygen from carbonate, hydroxyl and water.
The real compositions of Calcioancylite-(La), -(Ce) and -(Nd) (see Belovitskaya et al., 2013, Crystallography Reports 58, 216-219; Wang et al., 2023, Min. Mag. 87, 554-560) are intermediate between the calcioancylite-(REE) and kozoite-(REE) endmembers, with REE:Me2+ usually close to 3:1, but with a dominance of the calcioancylite-(REE) component.


 
5.DE.010. Schuilingite-(Nd)
 
Schuilingite-(Nd) PbCuNd(CO3)3(OH)·1.5H2O orth., P21cn A

Schuilingite-(Nd): Cu2+ in square-pyramidal, 5-fold coordination, Pb2+ in irregular 8-fold coordination (one distance is quite large and it is not clear whether or not it should be considered a bond), and REE in 10-fold coordination. The structure contains chains of face-sharing REE polyhedra, similar to chains in Gysinite-(Nd) (Schindler & Hawthorne, 1999, Can. Min. 37, 1463-1470).


 
5.DE.015. Sheldrickite
 
Sheldrickite NaCa3(CO3)2F3·H2O trig., P32 IMA 1996-019

Sheldrickite: layered structure on (001). One layer consists of of CO3 groups perpendicular to (001), Na polyhedra with Na in 8-fold coordination and H2O groups, the second layer of Ca polyhedra with Ca in 9-fold coordination and F anions (Grice et al., 1997, Can. Min. 35, 181-187).


 
5.DE.020. Alexkhomyakovite
 
Alexkhomyakovite K6(Ca3Na)(CO3)5Cl·6H2O hex., P63/mcm IMA 2015-013

Alexkhomyakovite: heteropolyhedral layers on (001), of disordered (Ca,Na) in 7-fold coordination (pentagonal bipyramids (Ca,Na)O5(H2O)2), interconnected via carbonate groups of two types, edge-sharing ones and vertex-sharing ones. 10-fold coordinated K cations centre KO5Cl(H2O)3 polyhedra on either side of the heteropolyhedral layer. A third type of carbonate group and Cl occupy the interlayer (Pekov et al., 2019, Eur. J. Min. 31, 135-143).


 
5.DE.025. Thomasclarkite
 
Thomasclarkite-(Y) NaY(HCO3)(OH)3·4H2O mon., P2 IMA 1997-047

Thomasclarkite-(Y): Na in irregular 6-fold and Y in 8-fold coordination (Grice & Gault, 1998, Can. Min. 36, 1293-1300).


 
5.DE.030. Kamphaugite
 
Kamphaugite-(Y) Ca2Y2(CO3)4(OH)2·3H2O tetr., P41212 IMA 1987-043

Kamphaugite-(Y): corrugated sheets parallel to (001), consisting of carbonate groups and polyhedra of Ca in 8-fold and Y in 9-fold coordination. The water content is not fully clear, chemical analysis gave 3 H2O per formula unit, whereas structure analysis gave 1 H2O (Rømming et al., 1993, Eur. J. Min. 5, 658-690).


 
5.DE.035. Peterbaylissite
 
Peterbaylissite Hg3(CO3)(OH)·2H2O orth., Pcab IMA 1993-041


 
5.DE.040. Clearcreekite
 
Clearcreekite Hg3(CO3)(OH)·2H2O mon., P21/c IMA 1999-003


 
5.DE.045. Szymanskiite
 
Szymanskiite Hg16Ni6(H3O)8(CO3)12(OH)12·3H2O hex., P63 IMA 1989-045



 
 
5.DF. Carbonates with additional tetrahedral anions: SO4, B(OH)4, PO4, AsO4
 
5.DF.005. Putnisite
 
Putnisite SrCa4Cr3+8(CO3)8(SO4)(OH)16·23H2O orth., Pnma IMA 2011106


 
5.DF.010. Nasledovite
 
Nasledovite PbMn3Al4(SO4)(CO3)4O5·5H2O Q


 
5.DF.015. Micheelsenite group [Ettringite group]
 
Micheelsenite (Ca,Y)6Al2(PO3OH)2(CO3)2(OH)12·24H2O hex., P63 IMA 1999-033
Imayoshiite Ca6Al2(B(OH)4)2(CO3)2(OH)12·24H2O hex., P63 IMA 2013-069
Chiyokoite Ca6Si2[(B(OH)4)(AsO3)](CO3)2(OH)12·24H2O hex., P63 IMA 2019-054


 
5.DF.020. Claraite
 
Claraite (Cu,Zn)15(CO3)4(AsO4)2(SO4)(OH)14·7H2O tric., ps.-hex. IMA 1981-023, Rd.






 
 

G = Grandfathered minerals: original description preceded the establishment of the CNMNC in 1959, and generally regarded as a valid species
A or IMA No. = Minerals approved by the CNMNC
Rd = Redefinition of the mineral approved by the CNMNC
Rn = Renamed with approval by the CNMNC
Q = Questionable mineral



Classification principles:
Subdivision of the Carbonates subclass "5.D: Carbonates with additional anions, with water" completely re-arranged compared to the chemical classification in Strunz 9. The subdivision is based now on structural aspects, the coordination polyhedra, corresponding roughly to the cation size (from smaller to larger cations): 5.DA. With cations only in tetrahedral coordination; 5.DB. With cations in tetrahedral + other coordination; 5.DC. With cations only in octahedral coordination; 5.DD. With cations in octahedral + other coordination; 5.DE. With cations in other coordination; 5.DF. Carbonates with additional tetrahedral anions: SO4, B(OH)4, PO4, AsO4.
Further classification:
5.DA. With cations only in tetrahedral coordination: No example known at time.
5.DB. With cations in tetrahedral + other coordination: Small cations in tetrahedral coordination; medium sized cations in tetrahedral coordination.
5.DC. With cations only in octahedral coordination: Small cations in octahedral coordination; medium-sized cations in octahedral coordination; large cations in octahedral coordination; minerals with unknown structure tentatively placed here.
5.DD. With cations in octahedral + other coordination: Medium-sized cations in octahedral + other cations in other coordination sorted according to increasing coordination number; large cations in octahedral + other cations in other coordination. Several minerals with unknown structure tentatively placed here.
5.DE. With cations in other coordination: Single coordination type, arranged with increasing coordination number; more than one coordination type, arranged with increasing coordination number (with few exceptions to show structural relations); other, non-polyhedral coordination: Hg in linear arrangement, including Hg-Hg bonds.
5.DF. Carbonates with additional tetrahedral anions: SO4, B(OH)4, PO4, AsO4: With SO4; with other tetrahedral anions.


To distinguish from classical Strunz numbering, on hierarchical "group" level, a numbering with 3 digits is used, like "5.DB.005. Niveolanite", instead of 2 digits (like "5.DB.05.") in the Strunz system.


© Thomas Witzke (2023)


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