| Dualite | |
|---|---|
| General | |
| Category | Silicate mineral, cyclosilicate |
| Formula (repeating unit) | 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] |
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]