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Combeite

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Formula:
Na2Ca2(Si6O18)0.5
Specific Gravity:
2.79 (Calculated)
Crystal System:
Trigonal
Name:
Named by T.G. Sahama and K. Hytönen, K. in 1957 in after Arthur Delmar Combe (24 December 1893 - 23 May 1949), geologist with the Geological Survey of Uganda, who contributed greatly to the geology of the Virunga volcanic field. The name should be pronounced koombite.
Lovozerite Group.

Fischer & Tillmanns (1983), who analyzed the crystal structure, report combeite as the high-temperature (> ca. 485oC) polymorph of the Na2Ca2Si3O9 phase, which syntetic counterpart having its composition varying from Na1.7Ca2.15Si3O9 to Na3.2Ca1.4Si3O9.


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Classification of CombeiteHide

Approved, 'Grandfathered' (first described prior to 1959)
9.CJ.15a

9 : SILICATES (Germanates)
C : Cyclosilicates
J : [Si6O18]12- 6-membered single rings (sechser-Einfachringe), without insular complex anions
61.1.2a.5

61 : CYCLOSILICATES Six-Membered Rings
1 : Six-Membered Rings with [Si6O18] rings; possible (OH) and Al substitution
14.6.1

14 : Silicates not Containing Aluminum
6 : Silicates of Ca with alkali or Mg or both

Physical Properties of CombeiteHide

Density:
2.79 g/cm3 (Calculated)

Optical Data of CombeiteHide

Type:
Uniaxial (+)
RI values:
nω = 1.598 nε = 1.598
Max Birefringence:
δ = 0.000
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Moderate

Chemical Properties of CombeiteHide

Formula:
Na2Ca2(Si6O18)0.5
IMA Formula:
Na2Ca2Si3O9
Idealised Formula:
Na2Ca2Si3O9
Common Impurities:
Ti,Zr,Al,Fe,Mn,Mg,Zn,Ba,K,F,Cl,S,P

Crystallography of CombeiteHide

Crystal System:
Trigonal
Class (H-M):
3m (3 2/m) - Hexagonal Scalenohedral
Space Group:
R3m
Setting:
R3m
Cell Parameters:
a = 10.429(2) Å, c = 13.149(3) Å
Ratio:
a:c = 1 : 1.261
Unit Cell V:
1,238.54 ų (Calculated from Unit Cell)
Z:
6
Comment:
data (space group & unit cell parameters) from Fischer & Tillmanns (1983)

Type Occurrence of CombeiteHide

Synonyms of CombeiteHide

Other Language Names for CombeiteHide

German:Combeit
Russian:Комбит
Spanish:Combeita

Relationship of Combeite to other SpeciesHide

Other Members of this group:
ImandriteNa12Ca3Fe3+2(Si6O18)2Orth.
KapustiniteNa5(Na,Mn2+)<1Zr(H2Si6O18)Mon. 2/m
KazakoviteNa6Mn2+Ti(Si6O18)Trig.
KoashviteNa6(Ca,Mn)(Ti,Fe)Si6O18 · H2OOrth.
LitvinskiteNa2(◻,Na,Mn)ZrSi6O12(OH,O)6Mon. m : Bm
LovozeriteNa2Ca(Zr,Ti)(Si6O12)[(OH)4O2] · H2OMon.
TisinaliteNa3H3(Mn,Ca,Fe)TiSi6(O,OH)18 · 2H2OTrig.
ZirsinaliteNa6(Ca,Mn2+,Fe2+)Zr(Si6O18)Trig.

Common AssociatesHide

Associated Minerals Based on Photo Data:
Aegirine9 photos of Combeite associated with Aegirine on mindat.org.
Nepheline9 photos of Combeite associated with Nepheline on mindat.org.
Sodalite5 photos of Combeite associated with Sodalite on mindat.org.
Wollastonite3 photos of Combeite associated with Wollastonite on mindat.org.
Glass1 photo of Combeite associated with Glass on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

9.CJ.05BazziteBe3Sc2(Si6O18)Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc
9.CJ.05BerylBe3Al2(Si6O18)Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc
9.CJ.05IndialiteMg2Al3(AlSi5O18)Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc
9.CJ.05StoppaniiteBe3Fe3+2(Si6O18) · H2OHex. 6/mmm (6/m 2/m 2/m) : P6/mcc
9.CJ.10Cordierite(Mg,Fe)2Al3(AlSi5O18)Orth. mmm (2/m 2/m 2/m) : Cccm
9.CJ.10Sekaninaite(Fe,Mg)2Al3(AlSi5O18)Orth.
9.CJ.15bImandriteNa12Ca3Fe3+2(Si6O18)2Orth.
9.CJ.15aKazakoviteNa6Mn2+Ti(Si6O18)Trig.
9.CJ.15cKoashviteNa6(Ca,Mn)(Ti,Fe)Si6O18 · H2OOrth.
9.CJ.15aLovozeriteNa2Ca(Zr,Ti)(Si6O12)[(OH)4O2] · H2OMon.
9.CJ.15aTisinaliteNa3H3(Mn,Ca,Fe)TiSi6(O,OH)18 · 2H2OTrig.
9.CJ.15aZirsinaliteNa6(Ca,Mn2+,Fe2+)Zr(Si6O18)Trig.
9.CJ.15aLitvinskiteNa2(◻,Na,Mn)ZrSi6O12(OH,O)6Mon. m : Bm
9.CJ.15aKapustiniteNa5(Na,Mn2+)<1Zr(H2Si6O18)Mon. 2/m
9.CJ.25BaratoviteKCa7(Ti,Zr)2Li3Si12O36F2Mon.
9.CJ.25KatayamaliteKLi3Ca7Ti2(SiO3)12(OH)2Mon. 2/m : B2/b
9.CJ.25AleksandroviteKCa7Sn2Li3Si12O36F2Mon. 2/m : B2/b
9.CJ.30DioptaseCuSiO3 · H2OTrig. 3 : R3
9.CJ.35KostyleviteK2Zr(Si3O9) · H2OMon.
9.CJ.40PetarasiteNa5Zr2(Si6O18)(Cl,OH) · 2H2OMon. 2/m : P21/m
9.CJ.45Gerenite-(Y)(Ca,Na)2(Y,REE)3Si6O18 · 2H2OTric.
9.CJ.50OdintsoviteK2Na4Ca3Ti2Be4Si12O38Orth.
9.CJ.55MathewrogersitePb7FeAl3GeSi12O36(OH,H2O)6Trig.
9.CJ.60PezzottaiteCs(Be2Li)Al2(Si6O18)Trig. 3 : R3

Related Minerals - Dana Grouping (8th Ed.)Hide

61.1.2a.1LovozeriteNa2Ca(Zr,Ti)(Si6O12)[(OH)4O2] · H2OMon.
61.1.2a.2KazakoviteNa6Mn2+Ti(Si6O18)Trig.
61.1.2a.3TisinaliteNa3H3(Mn,Ca,Fe)TiSi6(O,OH)18 · 2H2OTrig.
61.1.2a.4ZirsinaliteNa6(Ca,Mn2+,Fe2+)Zr(Si6O18)Trig.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

14.6.2PectoliteNaCa2Si3O8(OH)Tric. 1 : P1
14.6.3Pectolite-M2abcNaCa2[HSi3O9]
14.6.4DenisoviteCa2(K,Na)Si3O8(F,OH)2Mon.
14.6.5TokkoiteK2Ca4[Si7O18(OH)](OH,F)Tric.
14.6.6MountainiteKNa2Ca2[Si8O19(OH)] · 6H2OMon. 2/m : P2/b
14.6.7RhodesiteKHCa2Si8O19 · 5H2OOrth. mmm (2/m 2/m 2/m)
14.6.8MiseriteK1.5-x(Ca,Y,REE)5(Si6O15)(Si2O7)(OH,F)2 · yH2OTric.
14.6.9ÅkermaniteCa2Mg(Si2O7)Tet. 4 2m : P4 21m
14.6.10MonticelliteCaMgSiO4Orth.
14.6.11MerwiniteCa3Mg(SiO4)2Mon. 2/m : P21/b
14.6.12DiopsideCaMgSi2O6Mon. 2/m : B2/b
14.6.13Tremolite☐{Ca2}{Mg5}(Si8O22)(OH)2Mon. 2/m : B2/m

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for CombeiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Sahama, T.G., Hytönen, K. (1957) Götzenite and combeite, two new silicates from the Belgian Congo. Mineralogical Magazine: 31: 503-510.
Fleischer, M. (1958) New mineral names. American Mineralogist: 43: 790-798.
Fischer, R., Tillmanns, E. (1981) Die Kristallstruktur von Combeit; ein Cyclosilikat mit Sechserringen. Fortschritte der Mineralogie: 59: 45-46.
Fleischer, M., Burns, R.G., Cabri, L.J., Francis, C.A., Pabst, A. (1982) New mineral names. American Mineralogist: 67: 413-418.
Fischer, R.X., Tillmanns, E. (1983) Die Kristallstrukturen von natürlichem Na2Ca2Si3O9 vom Mt. Shaheru (Zaire) und aus dem Mayener Feld (Eifel). Neues Jahrbuch für Mineralogie - Monatshefte: 49-59.
Dunn, P.J., Grice, J.D., Fleischer, M., Pabst, A. (1984): New mineral names. American Mineralogist: 69: 214.
Ohsato, H., Maki, I., Takéuchi, Y. (1985) Structure of Na2CaSi2O6. Acta Crystallographica: C41: 1575-1577.
Ohsato, H., Takeuchi, Y., Maki, I. (1986) Structure of Na4Ca4[Si6O18]. Acta Crystallographica: C42: 934-937.
Fischer, R.X., Tillmanns, E. (1987) Revised data for combeite, Na2Ca2Si3O9. Acta Crystallographica: C43: 1852-1854.
Pekov, I.V., Krivovichev, S.V., Zolotarev, A.A., Yakovenchuk, V.N., Armbruster, T., Pakhomovsky, Y.A. (2009) Crystal chemistry and nomenclature of the lovozerite group. European Journal of Mineralogy: 21: 1061-1071.

Internet Links for CombeiteHide

Localities for CombeiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Democratic Republic of Congo (Zaïre)
 
  • Nord-Kivu
    • Goma
Andersen, T., Elburg, M. A., & Erambert, M. (2014). Extreme peralkalinity in delhayelite-and andremeyerite-bearing nephelinite from Nyiragongo volcano, East African Rift. Lithos, 206, 164-178.
Mineralogical Magazine 31 (1957) 698-699; Fischer, R.X. Tillmanns, E. (1983): Die Kristallstrukturen von natürlichem Na2Ca2Si3O9 vom Mt. Shaheru (Zaire) und aus dem Mayener Feld (Eifel), N. Jb. Mineral. Mh. 49-59.
Germany
 
  • Rhineland-Palatinate
    • Eifel
      • Mayen
        • Ettringen
          • Bellerberg volcano
            • Southern lava flow
              • Mayener Feld
Fischer, R.X. Tillmanns, E. (1983): Die Kristallstrukturen von natürlichem Na2Ca2Si3O9 vom Mt. Shaheru (Zaire) und aus dem Mayener Feld (Eifel), N. Jb. Mineral. Mh. 49-59.
Russia
 
  • Eastern-Siberian Region
    • Krasnoyarsk Territory (Krasnoyarsk Kray; Krasnoyarskii Krai)
      • Maimecha and Kotui Rivers Basin
Henderson, C. M. B., Kogarko, L. N., & Plant, D. A. (1999). Extreme closed system fractionation of volatile-rich, ultrabasic peralkaline melt inclusions and the occurrence of djerfisherite in the Kugda alkaline complex, Siberia. Mineralogical Magazine, 63(3), 433-438.
Tanzania
 
  • Arusha Region
www.koeln.netsurf.de/~w.steffens/other.htm; Henderson, C. M. B., Kogarko, L. N., & Plant, D. A. (1999). Extreme closed system fractionation of volatile-rich, ultrabasic peralkaline melt inclusions and the occurrence of djerfisherite in the Kugda alkaline complex, Siberia. Mineralogical Magazine, 63(3), 433-438.; Wiedenmann D, Zaitsev A N, Britvin S N, Krivovichev S V, Keller J (2009) Alumoåkermanite, (Ca,Na)2(Al,Mg,Fe2+)(Si2O7), a new mineral from the active carbonatite-nephelinite-phonolite volcano Oldoinyo Lengai, northern Tanzania. Mineralogical Magazine 73, 373-384
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