Emeleusite

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Emeleusite
Emeleusite-494126.jpg
Emeleusite (white crusts) from the island of Illutalik off Greenland (size: 2.4 cm × 1.8 cm × 1.1 cm)
General and classification
other names

IMA 1977-021

chemical formula Na 2 LiFe 3+ [Si 6 O 15 ]
Mineral class
(and possibly department) 		Silicates and germanates - chain and band silicates (inosilicates)
System no. to Strunz
and to Dana 		9.DN.05 ( 8th edition : VIII / E.22)
66.03.03.03
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Cmce (No. 64)Template: room group / 64
Lattice parameters a  = 14.00  Å ; b  = 17.34 Å; c  = 10.07 Å
Formula units Z  = 8
Physical Properties
Mohs hardness 5 to 6
Density (g / cm 3 ) measured: 2.76 (7); calculated: 2.81
Cleavage is missing
colour colorless, creamy pink
Line color White
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.596
n β  = 1.597
n γ  = 1.597
Birefringence δ = 0.001
Optical character biaxial negative

Emeleusite is a very rarely occurring mineral from the mineral class of "silicates and germanates" with the chemical composition Na 2 LiFe 3+ [Si 6 O 15 ] and is therefore chemically a sodium - lithium - iron - silicate , which structurally forms the chains - and band silicates counts.

Emeleusite crystallizes in the orthorhombic crystal system , but develops only tiny colorless or creamy-pink crystals up to about two millimeters in length with a tabular or twinned pseudohexagonal habit . It usually occurs in the form of granular mineral aggregates .

Etymology and history

Was first discovered in the Emeleusit Ilimaussaq - Intrusion in Kangerdluarssuq -Fjord near Narsaq ( kujalleq ) in the southwest of Greenland and described by Upton BGJ, PG Hill, O. Johnsen and OV Petersen that the mineral in honor of Dr. Charles Henry Emeleus from the University of Durham in England.

Type material of the mineral is made at the University of Copenhagen in Denmark; in the Geological Department of the University of Edinburgh in Scotland; Natural History Museum in London, Great Britain (catalog number 1987,118) and in the National Museum of Natural History in Washington, DC, USA (catalog number 146464).

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the emeleusite belonged to the mineral class of "silicates and germanates", but was wrongly listed in the department of "ring silicates (cyclosilicates)", where it was listed together with Almarudit , Armenit , Berezanskit , Brannockit , Chayesit , Darapiosit , Dusmatovit , Eifelit , Faizievit , Merrihueit , Milarit , Oftedalit , Osumilith , Osumilith- (Mg) , Poudretteit , Roedderit , Shibkovit , Sogdianit , Sugilith , Trattnerit , Yagiit , Yakovenchukit- (Y) the "Milarit-Osumilith-Gruppe" with the system no. VIII / E.22 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies emeleusite in the category of "chain and band silicates (inosilicates)". This is further subdivided according to the structure of the silicate chains or bands, so that the mineral, according to its structure, can be found in the sub-section "Chain and band silicates with 6-periodic double chains", where it is only found together with Tuhualite and Zektzerite the "Tuhualith group" with the system no. 9.DN.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns emeleusite to the class of "silicates and Germanates" and there in the department of "chain silicates: double unbranched chains, W = 2". Here he is in the " P = 6 (Tuhualith group) " with the system no. 66.03.04 can be found in the subsection “Chain Silicates : Double unbranched chains, W = 2 with chains P> 2”.

Crystal structure

Emeleusite crystallizes orthorhombically in the space group Cmce (space group no. 64) with the lattice parameters a  = 14.00  Å ; b  = 17.34 Å and c  = 10.07 Å and 8 formula units per unit cell . Template: room group / 64

Education and Locations

Emeleusit formed as part of an ancillary peralkaline trachyte - Dykes , in Aegirin - and albitreichen layers. In addition to those already mentioned, apatite , calcite , various mica , titanium-containing narsarsukite , zinc-containing nordite , pectolite , quartz , riebeckite , thorite and zirconium also appeared as accompanying minerals .

Apart from its type locality , the Ilimaussaq intrusion near Narsaq in Greenland, no other sites for emeleusite are known to date.

See also

literature

  • BGJ Upton, PG Hill, O. Johnsen, OV Petersen: Emeleusite: a new LiNaFeIII silicate from south Greenland . In: Mineralogical Magazine . tape 42 , 1978, pp. 31–34 ( rruff.info [PDF; 422 kB ]).
  • O. Johnsen, K. Nielsen, I. Sotofte: The crystal structure of emeleusite, a novel example of six-double chain . In: Journal of Crystallography . tape 147 , 1978, pp. 297–306 ( rruff.info [PDF; 386 kB ]).

Web links

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

Individual evidence

  1. ↑ a b c d 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.  651 .
  2. ↑ Webmineral - Emeleusite
  3. ↑ a b The former name of this group of rooms was Ccma .
  4. ↑ a b c Emeleusite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 72.9 kB )
  5. ↑ a b 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 .
  6. ↑ a b c d Mindat - Emeleusite
  7. ↑ Find location list for emeleusite at the Mineralienatlas and at Mindat