Lueshit

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Lueshit
Lueshite-md35a.jpg
Lueshite crystal from the type locality "Lueshe Mine", Kivu , Democratic Republic of the Congo (size: 0.6 × 0.6 × 0.6 cm)
General and classification
other names

Igdloit

chemical formula NaNbO 3
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.CC.30 ( 8th edition : IV / C.10)
03/04/03/04
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m 2 / m 2 / m
Room group (no.) Pbma (No. 57)
Lattice parameters a  = 5.57  Å ; b  = 15.52 Å; c  = 5.50 Å
Formula units Z  = 8
Physical Properties
Mohs hardness 5 to 5.5
Density (g / cm 3 ) measured: 4.44; calculated: [4.58]
Cleavage imperfect after {001}
Break ; Tenacity not defined
colour black, reddish brown to brownish purple
Line color Gray
transparency opaque, translucent edges
shine weak metallic luster
Crystal optics
Refractive index n  = 2.29 to 2.30
Optical character biaxial negative
Axis angle 2V = 46 to 90 °

Lueshite is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the composition NaNbO 3 , so from a chemical point of view it is a sodium - niobium oxide and known as a chemical compound sodium niobate .

Lueshite is generally opaque and usually develops cube-like or irregular octahedral crystals up to about 1.5 centimeters in size, black in color with gray streak color . However, thin corners and edges are reddish-brown to brown-violet and translucent.

Etymology and history

Lueshit was first discovered in the "Lueshe Mine", about 180 km north of Goma (North Kivu) in the Democratic Republic of the Congo and described in 1959 by Alexandre Safiannikoff , who named the mineral after its type of locality .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the syphilis belonged to the department of "Oxides with the molar ratio of metal: oxygen = 2: 3 (M 2 O 3 and related compounds)", where it, together with barioperovskite , Isolueshit , Latrappit , Loparit- (Ce) , Macedonit , Natroniobit , Perovskit , Tausonit and Uhligit (discredited 2006) the "Perovskite series" with the system no. IV / C.10 formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns the syphilis hit to the somewhat expanded section of "Oxides with the molar ratio of metal: oxygen = 2: 3, 3: 5 and comparable" a. However, this is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the subsection “With large and medium-sized cations”, where together with perovskite the “Perovskite-Lueshite group” is found with the System no. 4.CC.30 and the other members Barioperowskit, Lakargiit, Latrappit and Natroniobit forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the syphilis hit to the class of "oxides and hydroxides" and there into the category of "oxides". Here it is together with barioperovskite, isolueshite, lakargiite, latrappite, loparite (Ce), perovskite and tauonite in the " perovskite group " with the system no. 04.03.03 to be found in the subsection “Simple oxides with a cation charge of 3+ (A 2 O 3 )”.

Modifications and varieties

The compound NaNbO 3 is dimorphic and occurs naturally in addition to the orthorhombic crystallizing syphilis as cubic crystallizing isoluesite ; possibly also as monoclinic crystallizing natroniobite , although its mineral status is still questionable.

Education and Locations

Lueshite forms in niobium-containing calcite - carbonatites . As accompanying minerals may include dolomite , Eudialyt , Fersmit different, mica , Griceit , ilmenite , Lovozerit , perovskite , pyrochlore , sodalite , Steenstrupin , thorianite , ussingite , vermiculite , Villiaumit occur.

As a rare mineral formation, Lueshite has only been found at a few sites so far. Its type locality "Lueshe Mine" is the only known site in the Democratic Republic of the Congo.

Other previously known localities are the pits "Demix-Varennes" near Saint-Amable and "Poudrette" at Mont Saint-Hilaire in the Canadian province of Quebec, some Fund points in Ilimaussaq complex near Narsaq in Greenland, Afrikanda , kovdor , Lovozero and Sallanlatvi on the Russian Kola Peninsula and the "Vermiculite Mine" in Fremont County of the US state of Colorado.

Crystal structure

Lueshite crystallizes orthorhombically in the space group Pbma (space group no. 57) with the lattice parameters a  = 5.57  Å ; b  = 15.52 Å and c  = 5.50 Å and 8 formula units per unit cell .

See also

literature

  • A. Safiannikoff: Un nouveau minéral de niobium. In: Académie Royal des Sciences d'Outre-Mer. Bulletin des Séances. Volume 5 1959, pp. 1251-1255.
  • M. Fleischer: New mineral names. In: American Mineralogist. Volume 46, 1961, pp. 1004–1004 ( PDF 80.9 kB )
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 519 (first edition: 1891).

Web links

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

Individual evidence

  1. ↑ a b c d e 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.  200 .
  2. ↑ a b c Lueshite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( PDF 71.6 kB )
  3. ^ The minerals of the Democratic Republic of Congo. ( Memento of the original from May 29, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / euromin.w3sites.net
  4. ^ IMA / CNMNC List of Mineral Names; February 2013 (PDF 1.3 MB)
  5. ↑ a b List of localities for Lueshit in the Mineralienatlas and Mindat