Dualite is a very rare and complex mineral of the eudialyte group, its complexity being expressed in its formula Na
30(Ca,Na,Ce,Sr)
12(Na,Mn,Fe,Ti)
6Zr
3Ti
3MnSi
51O
144(OH,H
2O,Cl)
9.[2][3] The formula is simplified as it does not show the presence of cyclic silicate groups.
The name of the mineral comes from its dual nature: zircono- and titanosilicate at once. Dualite has two modules in its structure: alluaivite one and eudialyte one.[3] After alluaivite and labyrinthite it stands for third representative of the eudialyte group with essential titanium.[2]
| Dualite | |
|---|---|
| General | |
| Category | Silicate mineral, cyclosilicate |
| Formula | Na 30(Ca,Na,Ce,Sr) 12(Na,Mn,Fe,Ti) 6Zr 3Ti 3MnSi 51O 144(OH,H 2O,Cl) 9 |
| IMA symbol | Dua[1] |
| Strunz classification | 9.CO.10 |
| Dana classification | 64.1b.1.4 |
| Crystal system | Trigonal |
| Crystal class | Ditrigonal pyramidal (3m) H-M symbol: (3m) |
| Space group | R3m |
| Unit cell | a = 14.15, c = 60.72 [Å] (approximated); Z = 3 |
| Identification | |
| Color | Yellow |
| Crystal habit | Anhedral grains |
| Cleavage | None |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 5 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent or translucent |
| Density | 2.84 (measured), 2.81 (calculated; approximated) |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.61, nε = 1.61 (approximated) |
| Pleochroism | None |
| Ultraviolet fluorescence | No |
| References | [2][3] |
Occurrence and association
editDualite was found in peralkaline pegmatoid rock at Mt Alluaiv, Lovozero massif, Kola Peninsula Russia. It associates with aegirine, alkaline amphibole, cancrinite, eudialyte, K-Na feldspar, lamprophyllite, lomonosovite, lovozerite, nepheline, sodalite, sphalerite, villiaumite, and vuonnemite.[3]
Notes on chemistry
editNotes on crystal structure
editDualite has doubled c value when compared to ordinary eudialyte. Its structural framework has 24 layers.[3]
References
edit- ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- 1 2 3 Mindat, Dualite, http://www.mindat.org/min-27578.html
- 1 2 3 4 5 6 Khomyakov, A.P., Nechelyustov, G.N., and Rastsvetaeva, R.K., 2009: Dualite, Na30(Ca,Na,Ce,Sr)12(Na,Mn,Fe,Ti)6Zr3Ti3MnSi51O144(OH,H2O,Cl)9, a new zircono-titanosilicate with a modular eudialyte-like structure from the Lovozero alkaline Pluton, Kola Peninsula, Russia. Geology of Ore Deposits 50(7), 574-582
Further reading
edit- Johnsen, O., Ferraris, G., Gault, R.A., Grice, D.G., Kampf, A.R., and Pekov, I.V., 2003. The nomenclature of eudialyte-group minerals. The Canadian Mineralogist 41, 785-794
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