| Ephesite | |
|---|---|
 | |
| General | |
| Category | Phyllosilicate |
| Formula (repeating unit) | NaLiAl2(Al2Si2)O10(OH)2 |
| IMA symbol | Eph[1] |
| Strunz classification | 9.EC.20 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/c[2] also reported is a triclinic polytype[3] |
| Unit cell | a = 5.12, b = 8.853 c = 19.303 [Å]; beta = 95.08°; Z = 4 |
| Identification | |
| Color | Brownish pink, pearl gray, pale green |
| Crystal habit | Flakes |
| Twinning | Commonly twinned about [310] or [310] |
| Cleavage | Perfect on {001} |
| Tenacity | Brittle |
| Mohs scale hardness | 3.5–4 |
| Luster | Vitreous, pearly on cleavage |
| Diaphaneity | Translucent |
| Specific gravity | 2.984 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.592 - 1.595 nβ = 1.624 - 1.625 nγ = 1.625 - 1.627 |
| Birefringence | δ = 0.033 |
| 2V angle | 18° to 28° |
| Dispersion | r > v strong |
| References | [2][3][4] |
Ephesite is a rare member of the mica silicate mineral group, phyllosilicate. It is restricted to quartz-free, alumina rich mineral assemblages and has been found in South African deposits in the Postmasburg district as well as Ephesus, Turkey.[5]
- ^ 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.
- ^ a b Epesite data on Webmineral
- ^ a b Ephesite in the Handbook of Mineralogy
- ^ Ephesite on Mindat.org
- ^ Phillips, F. (1931) Ephesite (soda-maragrite) from the Postmasburg district, South Africa, Corpus Christi College, Cambridge, pp. 482-485