Dualite
| 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 |
| 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 | |
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. 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. After alluaivite and labyrinthite it stands for third representative of the eudialyte group with essential titanium.