| Greenalite | |
|---|---|
 Greenalite (green) with galena and siderite, from Spain | |
| General | |
| Category | Phyllosilicates Kaolinite-serpentine group |
| Formula (repeating unit) | (Fe2+,Fe3+)2-3Si2O5(OH)4 |
| IMA symbol | Gre[1] |
| Strunz classification | 9.ED.15 |
| Crystal system | Monoclinic |
| Crystal class | Domatic (m) (same H-M symbol) |
| Space group | Cm |
| Unit cell | a = 5.54, b = 9.55 c = 7.44 [Å]; β = 104.2°; Z = 2 |
| Identification | |
| Color | Green, light yellow-green |
| Crystal habit | Rare minute crystals, rounded grains common; as porphyroblasts, oolites |
| Cleavage | None |
| Mohs scale hardness | 2.5 |
| Luster | Dull, earthy |
| Streak | Greenish-gray |
| Diaphaneity | Translucent to subopaque |
| Specific gravity | 2.85 - 3.15 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.650 - 1.675 nβ = 1.674 nγ = 1.674 |
| Birefringence | δ = 0.024 |
| Pleochroism | X = pale yellow, Y and Z = green |
| Other characteristics | Magnetic |
| References | [2][3][4] |
Greenalite is a mineral in the kaolinite-serpentine group with the chemical composition (Fe2+,Fe3+)2-3Si2O5(OH)4.[2][5] It is a member of the serpentine group.[3]
- ^ 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 Handbook of Mineralogy
- ^ a b Greenalite on Mindat.org
- ^ Greenalite on Webmineral
- ^ Sleep N.H., Bird D.K. (2007): Niches of the pre-photosynthetic biosphere and geologic preservation of Earth’s earliest ecology. Geobiology 5, 101-117