Biotite
| Biotite | |
|---|---|
 Thin tabular biotite aggregate (Image width: 2.5 mm) | |
| General | |
| Category | Darkmicaseries |
| Formula (repeatin unit) | K(Mg,Fe) 3(AlSi 3O 10)(F,OH) 2 |
| Creestal seestem | Monoclinic(2/m) Space Group: C 2/m |
| Identification | |
| Formula mass | 433.53 g |
| Colour | Mirk broun, greenish-broun, blackish-broun, yellae, white |
| Creestal habit | Massive tae platy |
| Twinnin | Common on the [310], less common on the {001} |
| Cleavage | Perfect on the {001} |
| Fractur | Micaceous |
| Tenacity | Brickle tae souple, elastic |
| Mohs scalehaurdness | 2.5–3.0 |
| Skinkle | Vitreous tae pearly |
| Streak | White |
| Diaphaneity | Skyre tae leamin tae opaque |
| Speceefic gravity | 2.7–3.1 |
| Density | 2.8–3.4 |
| Optical properties | Biaxial (-) |
| Refractive index | nα= 1.565–1.625 nβ= 1.605–1.675 nγ= 1.605–1.675 |
| Birefringence | δ = 0.03–0.07 |
| Pleochroism | Strong |
| Dispersion | r < v (Fe rich); r > v weak (Mg rich) |
| Ultravioletfluorescence | None |
| References | [1][2][3] |
Biotiteis a commonphyllosilicatemeeneralathin themicagroup, wi the approximate chemical formulaK(Mg,Fe)
3AlSi
3O
10(F,OH)
2.Mair generally, it refers tae the dark mica series, primarily asolid-solutionseries atween the iron-endmemberannite,an the magnesium-endmemberphlogopite;mair aluminous endmembers includesiderophyllite.Biotite wis named biJ.F.L. Hausmannin 1847 in honour o the FrenchpheesicistJean-Baptiste Biot,who, in 1816, researched the optical properties omica,discovering mony unique properties.[4]
Biotite is a sheetsilicate.Airn,magnesium,aluminium,silicon,oxygen,anhydrogenfurm sheets that are waikly boond thegither bipotassiumions. It is whiles cried "iron mica" acause it is mair airn-rich nor phlogopite. It is an aa whiles cried "black mica" as opponed tae "white mica" (muscovite) – baith furm in some rocks, in some instances side-bi-side.
References
[eedit|eedit soorce]- ↑Biotite mineral information and data Mindat
- ↑Biotite Mineral Data Webmineral
- ↑Handbook of Mineralogy
- ↑Johann Friedrich Ludwig Hausmann (1828).Handbuch der Mineralogie.Vandenhoeck und Ruprecht. p. 674."Zur Bezeichnung des sogenannten einachsigen Glimmers ist hier der Name Biotit gewählt worden, um daran zu erinnern, daß Biot es war, der zuerst auf die optische Verschiedenheit der Glimmerarten aufmerksam machte." (For the designation of so-called uniaxial mica, the name "biotite" has been chosen in order to recall that it was Biot who first called attention to the optical differences between types of mica.)