Annite (mineral)

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Annit
Annite-pas-130ab.jpg
Annit from Rockport , Essex County , Massachusetts , USA
General and classification
chemical formula KFe 2+ 3 [(OH, F) 2 | AlSi 3 O 10 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.EC.20 ( 8th edition : VIII / H.11)
71.02.02b.3
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 5.3860  Å ; b  = 9.3241 Å; c  = 10.2683 Å
β  = 100.63 °
Formula units Z  = 2
Physical Properties
Mohs hardness 2.5 to 3
Density (g / cm 3 ) measured: 3.3; calculated: [3.36]
Cleavage completely after {001}
colour black, reddish brown
Line color brownish white
transparency transparent to translucent
shine Glass gloss, pearlescent gloss
Crystal optics
Refractive indices n α  = 1.625 to 1.631
n β  = 1.690
n γ  = 1.691 to 1.697
Birefringence δ = 0.066
Axis angle 2V = 0 ° to 5 °
Pleochroism in the X direction brown, in the Y and Z directions dark brown

Annite is a rather rare mineral from the mica group within the mineral class of silicates and germanates . It crystallizes in the monoclinic crystal system with the chemical composition KFe 2+ 3 [(OH, F) 2 | AlSi 3 O 10 ] and is therefore chemically a potassium - iron - aluminosolicate with additional fluorine and / or hydroxide ions . Structurally, annite belongs to the layered silicates (phyllosilicates).

Annite is transparent to translucent and usually develops tabular crystals and leafy mineral aggregates of black color with a reddish sheen. Depending on the characteristics, the crystal surfaces have a glass-like or mother-of-pearl-like sheen .

Etymology and history

The mineral was already described in 1868 by James Dwight Dana in his sixth edition of Dana's system of mineralogy , in which he also established the systematics of minerals according to Dana . Annit was named after its first site ( type locality ), Cape Ann on the eastern headland of Essex County in Massachusetts , USA .

classification

Already in the outdated but still partially in use 8th edition of the mineral classification by Strunz of Annite belonged to the mineral class of "silicates and Germanates" and then to the Department of " phyllosilicates (phyllosilicates)" where he collaborated with Aspidolith , Eastonit , Ephesit , Fluorannit , fluorophlogopite , Hendricksit , Masutomilith , Montdorit , Norrishit , phlogopite , polylithionite , Preiswerkite , Shirokshinit , Shirozulith , Siderophyllit , Sokolovait , Tainiolith , Tetraferriannit , Tetraferriphlogopit , Trilithionite and Voloshinit the "Lithionit biotite series" with the system number VIII / H.11 educated.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies the annit in the “phyllosilicates” department. This is, however, further subdivided according to the layer structure, so that the mineral can be found according to its structure in the sub-section “ with mica tablets, composed of tetrahedral and octahedral nets”, where it can be found together with aspidolite, biotite (mixed crystal), eastonite, ephesite, fluorannite , fluorophlogopite, Hendricksit, lepidolite (solid solution), Masutomilith, Norrishit, phlogopite, Polylithionit, Preiswerkite, Shirokshinit, Shirozulith, Siderophyllit, Sokolovait, Suhailit, Tetraferriannit, Tetraferriphlogopit, Trilithionite, Wonesit and zinnwaldite (solid solution) which is now named "Phlogopitgruppe" with the System no. 9.EC.20 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the annit to the class of "silicates and germanates" and there in the department of "layered silicate minerals (phyllosilicates)". Here it is in the " mica group (biotite subgroup) " with the system no. 71.02.02b.

Chemism

In an examination of two annite samples, small amounts of magnesium oxide were found in one sample, a slightly higher proportion of aluminum was found in another sample, but the fluorine and hydroxide groups were missing .

Crystal structure

Annite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 5.3860  Å , b  = 9.3241 Å and c  = 10.2683 Å and two formula units per unit cell . Template: room group / 12

Education and Locations

Annit

The type locality is, as described above, on Cape Ann, Massachusetts, USA.

There are a total of (as of 2015) 366 locations of Annit.

In Germany , in Rhineland-Palatinate, there is a site in Rockeskyll near Gerolstein on the Eifel . There are also two sites in Saxony , both in Upper Lusatia : One is in Thiemendorf , Waldhufen municipality , the other in Döbschütz , Vierkirchen municipality .

In Austria there is a site in Styria in the Gleinalpe mountain range . There may be another site in Amering in the Murtal district .

In Switzerland there are two sites. One is in Chironico in the canton of Ticino . The other is in Thyon in the canton of Valais .

Otherwise the mineral can be found in Egypt , Argentina , Australia , Brazil , China , Eritrea , Finland , Greece , India , Italy , Japan , Cameroon , Canada , Madagascar , Malawi , Mongolia , Niger , Norway , the Philippines , Poland , Portugal , Romania , Russia , St. Lucia , Slovakia , South Africa , Spain , Sweden , the Czech Republic , the United Kingdom , Ukraine , Hungary, and the United States can be found. The mineral is thus represented in 34 countries and on all continents .

properties

Annit is part of biotite . Biotite was revoked its status as an independent material in 1999; it is now treated as a mixed crystal in the annite- phlogopite mixed series .

Annit also has pleochroism . It appears brown in the X direction, but dark brown in the Y and Z directions.

See also

literature

  • David R. Wones: Physical properties of synthetic biotites on the join phlogopite-annite. In: American Mineralogist , Vol. 48, 1963, pp. 1300-1321
  • Embaie Ferrow: Mössbauer and X-ray studies on the oxidation of annite and ferriannite. In: Physics and Chemistry of Minerals. , Volume 14, 1987, Springer Verlag, pp. 270-275, doi : 10.1007 / BF00307993

Web links

Commons : Annite  - collection of images, videos and audio files

Individual evidence

  1. ^ A b Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  667 .
  2. ↑ a b c Mindat - Annite (English)
  3. ↑ a b c d e f g h i Annite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (eds.): Handbook of Mineralogy, Mineralogical Society of America, 2001 ( PDF 66.9 kB ).
  4. ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 252 ( Dörfler Natur ).
  5. ↑ Mineralienatlas: Annit
  6. ↑ a b c d e Mindat - Locations of Annite (English)
  7. ↑ Mineral Atlas: Biotite