Eudialyte
| Eudialyte | |
|---|---|
| General | |
| Category | Cyclosilicate |
| Formula | Na15Ca6(Fe,Mn)3Zr3SiO(O,OH,H2O)3 (Si3O9)2(Si9O27)2(OH,Cl)2 |
| IMA symbol | Eud |
| Strunz classification | 9.CO.10 |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (3 2/m) |
| Space group | R3m |
| Unit cell | a = 14.31, c = 30.15 [Å]; Z = 12 |
| Identification | |
| Color | Red, magenta, brown; also blue and yellow |
| Crystal habit | Crystals short rhombohedral to long prismatic, granular, irregular masses |
| Cleavage | Distinct on {0001} imperfect on {1120} |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 5–6 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 2.74–3.10 |
| Optical properties | Uniaxial (+/−) |
| Refractive index | nω = 1.606–1.610 nε = 1.610–1.613 |
| Birefringence | δ = 0.004 |
| Pleochroism | Weak: O= colorless, pale yellow, pink; E= pink to colorless |
| Solubility | H2SO4 |
| Other characteristics | Mildly Radioactive |
| References | |
Eudialyte, whose name derives from the Greek phrase Εὖ διάλυτος, eu dialytos, meaning "well decomposable", is a somewhat rare, nine-member-ring cyclosilicate mineral, which forms in alkaline igneous rocks, such as nepheline syenites. Its name alludes to its ready solubility in acid.
Eudialyte was first described in 1819 for an occurrence in nepheline syenite of the Ilimaussaq intrusive complex of southwest Greenland.