Eudialyte
| Eudialyte | |
|---|---|
 |
|
| General | |
| Category | Cyclosilicate |
|
Formula (repeating unit) |
Na15Ca6(Fe,Mn)3Zr3SiO(O,OH,H2O)3 (Si3O9)2(Si9O27)2(OH,Cl)2 |
| Strunz classification | 9.CO.10 |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (3 2/m) |
| Space group | R3m |
| 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.
Eudialyte is used as a minor ore of zirconium. Another use of eudialyte is as a minor gemstone, but this use is limited by its rarity, which is compounded by its poor crystal habit. These factors make eudialyte of primary interest as a collector's mineral. Eudialyte typically has a significant content of U, Pb, Nb, Ta, Zr, Hf, and rare earth elements (REE). Because of this, it is very common geoscientists use eudialyte as a geochronometer to date and investigate the genesis of the host rocks.
Eudialyte is found associated with other alkalic igneous minerals, in addition to the some minerals common to most igneous material in general.
Associate minerals include: microcline, nepheline, aegirine, lamprophyllite, lorenzenite, catapleiite, murmanite, arfvedsonite, sodalite, aenigmatite, rinkite, låvenite, titanite and titanian magnetite.
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