Eastonite
| Eastonite | |
|---|---|
 |
|
| General and classification | |
| chemical formula |
|
|
Mineral class (and possibly department) |
Silicates and germanates - layered silicates (phyllosilicates) |
|
System no. to Strunz and to Dana |
9.EC.20 ( 8th edition : VIII / H.11) 71.02.02b.05a |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic |
| Space group | C 2 / c (No. 15) |
| Physical Properties | |
| Mohs hardness | 2 to 3 |
| Density (g / cm 3 ) | Please complete |
| Cleavage | perfectly |
| colour | gray-green, yellow-brown, brown-red, black |
| Line color | white to off-white |
| transparency | Please complete |
| shine | Please complete |
Eastonite is a very rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the monoclinic crystal system with the idealized chemical composition KAlMg 2 (Si 2 Al 2 ) O 10 (OH) 2 , so it is a potassium - magnesium - aluminum silicate with additional hydroxide ions .
However, natural eastonite forms a mixed crystal row with the iron analogue siderophyllite (KFe 2+ 2 Al [(OH) 2 | Al 2 Si 2 O 10 ]) . In addition, the hydroxide group can also be partially replaced ( substituted ) by fluorine . The formula for eastonite is therefore given in various sources as K (Mg, Fe 2+ ) 2 Al [(OH, F) 2 | Al 2 Si 2 O 10 ].
Eastonite belongs to the extensive mica group and there to the so-called " real mica ". Structurally, the mineral is one of the phyllosilicates ( phyllosilicates ).
Due to the mixed crystal formation with siderophyllite, but also with other mica minerals and serpentines , eastonite is predominantly found in mineral aggregates with fibrous, flaky or blocky formation and the sparkling shine that is typical of mica . Its color also varies accordingly between gray-green, yellow-brown, brown-red and black.
Etymology and history
Eastonite was first discovered in 1904 by Eyerman on Chestnut Hill near Easton in Northampton County of the US state of Pennsylvania and described in 1925 by Alexander Newton Winchell , who named the mineral after its type locality .
classification
Already in the outdated, but partly still in use 8th edition of the mineral systematics according to Strunz , eastonite belonged to the mineral class of "silicates and germanates" and there to the department of "phyllosilicates", where it was used together with annite , aspidolite , ephesite , fluorannite , 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 within the mica group.
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 eastonite in the category of "phyllosilicates". However, this is further subdivided according to its composition, so that the mineral can be found in the sub-section "Layered silicates (phyllosilicates) with mica sheets, composed of tetrahedral and octahedral networks", where it can be found together with annite, aspidolite, biotite (mineral group), ephesite , Fluorannit, fluorophlogopite, Hendricksit, lepidolite (mineral group), Masutomilith, Norrishit, phlogopite, polylithionite, Preiswerkite, Shirokshinit, Shirozulith, Siderophyllit, Sokolovait, Suhailit , Tetraferriannit, Tetraferriphlogopit, Trilithionite, Wonesit and zinnwaldite (mineral group) the "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 eastonite to the class of "silicates and germanates" and there in the department of "layered silicate minerals". Here it is in the " mica group (biotite subgroup) " with the system no. 71.02.02b can be found in the subsection “ Layered Silicates: Layers of six-membered rings with 2: 1 layers”.
Education and Locations
Like other mica, eastonite is found more frequently in igneous , metamorphic and sedimentary rocks , but so far only very few sites are known in which eastonite could be detected with a composition that comes close to the idealized formula.
Besides its type locality Chestnut Hill, or more precisely the quarry CK Williams & Co., in the United States, this is still a granite - Intrusion at the Tavarekere-Kengere Road near Bangalore in India, the pit "Agassiz" at Lynn Lake in the Canadian province of Manitoba , an eclogite storage near Liset (municipality Stad ) in the Norwegian province of Sogn og Fjordane and an abandoned waste dump of a former mine near Šluknov- Rožany ( Rosenhain ) in the Czech region of Ústecký kraj.
Crystal structure
Eastonite crystallizes monoclinically in the space group C 2 / c (space group no. 15) , whereby the lattice parameters have not yet been determined.
See also
literature
- AN Winchell : Studies in the mica group - Part 1. In: American Journal of Science. Volume 9 (1925), pp. 309–327 ( PDF 805.5 kB ; p. 8)
- Kenneth JT Livi, David R. Veblen: "Eastonite" from Easton, Pennsylvania: A mixture of phlogopite and a new form of serpentine. In: American Mineralogist. Volume 72 (1987), pp. 113–125 ( PDF 1.6 MB )
- Milan Rieder, Giancarlo Cavazzini, Yurii D'Yakonov, Viktor A. Frank-Kamenetskii, Glauco Gottardt, Steven Guggenheim, Pavel V. Koval, Georg Müller, Ana MR Neiva, Edward W. Radoslovich, Jean-Louis Robert, Francesco P. Sassi , Hiroshi Takeda, Zdeněk Weiss, David R. Wones: Nomenclature of the micas. In: The Canadian Mineralogist. Volume 36 (1998), pp. 905-912 ( PDF 573.9 kB )
Web links
- Mineral Atlas: Eastonite (Wiki)
- Mindat - Eastonite
- Web mineral - Eastonite
- Database-of-Raman-spectroscopy - Eastonite
Individual evidence
- ↑ a b IMA / CNMNC List of Mineral Names; March 2018 ( Memento from June 11, 2018 in the Internet Archive ) (PDF 1.65 MB)
- ^ A b c Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 667 .
- ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
- ↑ Find location list for Eastonite at the Mineralienatlas and at Mindat