Paraumbit

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Paraumbit
Paraumbite.jpg
White, pearly paraumbit crust on pink eudialyte from Eweslogtschorr, Chibinen , Kola Peninsula, Russia
General and classification
other names

IMA 1982-007

chemical formula
  • K 3 (H 3 O) Zr 2 [S 3 O 9 ] 2 · ≈2H 2 O
  • K 3 Zr 2 H [Si 3 O 9 ] 2 • 3H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates - chain silicates and band silicates (inosilicates)
System no. to Strunz
and to Dana 		9.DG.25 ( 8th edition : VIII / F.20)
59.02.01.02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-pyramidal; mm 2
Space group P 2 cm (No. 28, position 5)Template: room group / 28.5
Lattice parameters a  = 10.34  Å ; b  = 13.29 Å; c  = 14.55 Å
Formula units Z  = 4
Physical Properties
Mohs hardness 4.5
Density (g / cm 3 ) measured: 2.59; calculated: 2.92
Cleavage completely mica-like after {010}; imperfect after {100} and {110}
Break ; Tenacity uneven
colour colorless, white to silvery white, gray, light green, pale yellow
Line color White
transparency transparent to translucent
shine Glass luster, pearlescent luster on cleavage surfaces
Crystal optics
Refractive indices n α  = 1.588
n β  = 1.601
n γ  = 1.610
Birefringence δ = 0.022
Optical character biaxial negative
Axis angle 2V = 82 ° (measured); 78 ° (calculated)

Paraumbit is a very rare mineral from the mineral class of "silicates and germanates" with the chemical composition K 3 (H 3 O) Zr 2 [S 3 O 9 ] 2 · ≈2H 2 O and is therefore chemically a water-containing potassium - Oxonium - Zirconium - Silicate .

Paraumbit crystallizes in the orthorhombic crystal system and develops isometric crystals up to about a millimeter in size, but also occurs in coarse masses.

In its pure form it is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also be translucent white to silvery white and, due to foreign admixtures, take on a gray, light green or pale yellow color.

Etymology and history

Paraumbit on was first discovered in a natrolite - passage on the southern slopes of the Eweslogtschorr ( Eveslogchorr ) in the Khibiny Mountains in the Murmansk Oblast on the Russian peninsula Kola . The mineral was described in 1983 by AP Khomyakov, AA Voronkov, Yu. S. Kobyashev and LI Polezhaeva, who named the mineral based on the close structural similarity to the mineral umbit . The lattice parameters a and b of the two minerals are almost identical, but the lattice parameter c for Paraumbit is twice as long as that of Umbit, which is expressed with the Greek prefix παρά para .

Type material of the mineral is in the Geological Museum of the Science Center of the Russian Academy of Sciences in Apatity on Kola under the catalog no. 5842 and 5843 ; in the Mineralogical Museum of the University of Saint Petersburg under catalog no. 17065 ; at the Mining Institute in Saint Petersburg under catalog no. 1630/1 ; in the Mineral Preserve Museum in Miass under catalog no. 13095vr and in the Fersman Museum in Moscow under catalog no. 82760 , vis3464 , vis4544 , vis4545 and vis5045 .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the paraumbit belonged to the mineral class of "silicates and germanates" and there to the department of "chain silicates and band silicates (inosilicates)", where together with umbit it belongs to the unnamed group VIII /F.20 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), also classifies the Paraumbit in the “chain and band silicates” department. However, this is further subdivided according to the structure of the chains, so that the mineral can be found according to its structure in the sub-section "Chain and band silicates with 3-periodic single and multiple chains", where it is also group 9 together with Umbit . DG.25 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the paraumbit to the class of "silicates and germanates", but there in the category of "ring silicates: triple rings". Here he is together with Umbit and Kostylevit in the group "Umbit and allied species" with the system no. 59.02.01 to be found in the subsection " Ring Silicates: Water-Containing Triple Rings ".

Crystal structure

Paraumbit crystallizes orthorhombically in the space group P 2 cm (space group no. 28, position 5) with the lattice parameters a  = 10.34  Å ; b  = 13.29 Å; c  = 14.55 Å and 4 formula units per unit cell . Template: room group / 28.5

Education and Locations

In the Khibiny Mountains to Paraumbit formed by displacement of Wadeit in pegmatite . In addition to wadeit, the accompanying minerals also include eudialyte , gaidonnayite , potassium feldspar , natrolite and pectolite .

In addition to its type locality Eweslogtschorr and the local wadeit occurrence, the mineral appeared in Russia on Mount Koaschwa and in the river valley of the Vuonnemiok in the Chibinen.

In the quarry Poudrette at Mont Saint-Hilaire in the southwest of the Canadian province of Quebec is Paraumbit found along with Gaidonnayit in converted pegmatite and sodalite - xenoliths in alkaline intrusive gabbro - syenite complex.

In addition, the mineral has so far only been discovered at Magnet Cove in Hot Spring County in the US state of Arkansas (as of 2017).

See also

literature

  • AP Khomyakov, AA Voronkov, Yu. S. Kobyashev, LI Polezhaeva: Umbite and paraumbite, new zirconosilicates of potassium from the Khibina alkalic massif . In: Zapiski Vserossijskogo Mineralogicheskogo Obshchestva . tape 112 , 1983, pp. 461-469 .
  • Pete J. Dunn, Michael Fleischer, Carl A. Francis, Richard H. Langley, Stephen A. Kissin, James E. Shigley, David A. Vanko, Janet A. Zilczer: New Mineral Names . In: American Mineralogist . tape 69 , 1984, pp. 810–815 ( minsocam.org [PDF; 742 kB ; accessed on November 30, 2017]).

Web links

Commons : Paraumbit  - 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.  638 .
  2. ↑ IMA / CNMNC List of Mineral Name; September 2017 (PDF 1.67 MB)
  3. ↑ a b c d e f g h Paraumbite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 77  kB ; accessed on November 30, 2017]).
  4. ↑ 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 .
  5. ↑ a b c d e Mindat - Paraumbite (English)
  6. ↑ Mineral Atlas : Type locality Eweslogchorr (Eveslogchorr), Chibiny (Khibiny), Kola Peninsula, Northwestern Federal District
  7. ↑ Find location list for Paraumbit at the Mineralienatlas and at Mindat