Bazzit

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Bazzit
Bazzite-184999.jpg
A bazzite crystal about 2 mm long on albite and orthoclase from the type locality "Seula Mine", Mount Camoscio, Oltrefiume, Baveno, Piedmont, Italy
General and classification
chemical formula Be 3 (Sc, Fe 3+ , Mg) 2 Si 6 O 18 · Na 0.32 · nH 2 O

(Sc, Al, Fe) 2 Be 3 [Si 6 O 18 ]

Mineral class
(and possibly department) 		Please complete!
System no. to Strunz
and to Dana 		9.CJ.05 ( 8th edition : VIII / E.12)
61.01.01.02
Similar minerals Aquamarine , Haüyn , kyanite , sapphire , blue tourmaline (indigolite)
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Space group P 6 / mcc (No. 192)Template: room group / 192
Lattice parameters a  = 9.51  Å ; c  = 9.11 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 6.5 to 7
Density (g / cm 3 ) measured: 2.77 to 2.8; calculated: 2.82
Cleavage imperfect after {0001}
Break ; Tenacity shell-like, uneven, brittle
colour light to dark blue
Line color White
transparency translucent to transparent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.622 to 1.637
n ε  = 1.602 to 1.622
Optical character uniaxial negative
Pleochroism ω = light greenish yellow; ε = intense sky blue

The mineral bazzite is a rarely occurring ring silicate from the beryl group. It crystallizes in the hexagonal crystal system with the composition Be 3 (Sc, Fe 3+ , Mg) 2 Si 6 O 18 · Na 0.32 · nH 2 O and is therefore chemically a water-containing beryllium ring silicate. The elements scandium , aluminum and iron indicated in the round brackets can represent each other in the formula , but are always in the same proportion to the other components of the mineral.

Bazzit mostly develops translucent, prismatic to columnar crystals up to about 2 cm in length with a hexagonal habit , but also radial mineral aggregates of light blue to dark blue color with white streak color . With a Mohs hardness of 6.5 to 7, bazzite is one of the hard minerals that, like the reference mineral quartz (7), is able to scratch simple window glass.

Etymology and history

Bazzit was first discovered in the "Seula Mine" on Monte Camoscio near Oltrefiume (municipality of Baveno ) in the Italian region of Piedmont and described in 1915 by E. Artini, who named the mineral after its discoverer Alessandro Eugenio Bazzi (1862–1929).

classification

Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the bazzite belonged to the mineral class of "silicates and germanates" and there to the department of " ring silicates (cyclosilicates)", where together with beryl , cordierite , indialite , pezzottaite , Sekaninait and Stoppaniit formed a separate 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 assigns the bazzit to the class of "silicates and germanates" and there in the section of " ring silicates (cyclosilicates)". This division is, however, further subdivided according to the type of ring formation, so that the mineral, according to its structure, can be found in the sub-division "[Si 6 O 18 ] 12− six-single rings without island-like, complex anions ", where it can only be found together with Beryl, indialite, pezzottaite and stoppaniite the "beryl group" with the system no. 9.CJ.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the bazzit to the class of "silicates and Germanates", but there it is in the more finely divided division of "ring silicates: six rings". Here he is also a member of the "beryl group" with the system no. 61.01.01 and the other members beryl, indialite, stoppaniite and pezzottaite within the subdivision of " ring silicates: six rings with Si 6 O 18 rings; possible (OH) and Al substitution ”.

Crystal structure

Bazzit crystal from the mountain Fibbia in the Swiss Gotthard massif, grown perfectly hexagonally (image width: 2.6 mm)

Bazzit crystallizes hexagonally in the space group P 6 / mcc (space group no. 192) with the lattice parameters a  = 9.51  Å and c  = 9.11 Å as well as two formula units per unit cell . Template: room group / 192

Education and Locations

Bazzite crystal, grown in the bedrock of the Gjaidtroghöhe in the Großer Fleißtal, Austria. Overall
size of the step: 8.7 × 4.9 × 3.6 cm

Bazzit formed by hydrothermal processes in alpinotype, scandium pegmatite - transitions and miarolitischen clefts in the granite . Accompanying minerals include albite , bavenite , beryl , calcite , chlorite , fluorite , hematite , laumontite , muscovite , orthoclase and quartz .

As a rare mineral formation, Bazzite could so far (status: 2011) only be proven at a few sites, of which about 40 can be considered known. In addition to its type locality "Seula Mine", the mineral also appeared in Italy in the municipality of Cuasso al Monte in Lombardy and near Agrano ( Omegna ) in Piedmont. Another location at Petit Mont Blanc in Val Veny is still questionable.

Tørdal in the Norwegian municipality of Drangedal , where up to two centimeters long crystals were found, is worth mentioning due to the unusual bazzite finds .

In Germany, the mineral was found in the Steinerleinbach quarry near Röhrnbach , near Saldenburg -Matzersdorf and Tittling -Stützersdorf in Bavaria and on Firstenstein near Königshain, on the A 4 motorway tunnel near Thiemendorf and on the Neuland quarry near Döbschütz in Saxony.

In Austria, Bazzit has so far only been found at the Gjaidtroghöhe in the Großer Fleißtal in Carinthia. In Switzerland, the mineral appeared at Lake Oberaar in Bern, in the Grisons municipality of Tujetsch , in several places in the Gotthard massif in Ticino, in the Etzlital and near Gurtnellen in the canton of Uri and in several places in the canton of Valais .

Other locations are in France, Japan, Kazakhstan, Russia and the United States.

See also

literature

  • H. Huttenlocher, Th. Hügi, W. Nowacki: X-ray and spectrographic examinations on the Bazzit vom Val Strem (Canton of Graubünden, Switzerland) . In: Experentia . tape 10 , no. 9 September 1954, p. 366-367 , doi : 10.1007 / BF02160538 .
  • New Mineral Names . In: American Mineralogist . tape 40 , 1955, pp. 370 ( minsocam.org [PDF; 272 kB ; accessed on June 15, 2018]).
  • American Mineralogist , 52, 563-564 (1967).
  • Tschermaks Mineralogische und Petrographische Mitteilungen / NF Vol. 35, pp. 410-421, ISSN  0369-1497 .
  • Canadian Mineralogist , Vol. 38 (2000), pp. 1419-1424, ISSN  0008-4476 .
  • Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 1244 .

Web links

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

Individual evidence

  1. ↑ a b IMA / CNMNC List of Mineral Names; March 2018 (English, PDF 1.65 MB; Bazzite see p. 19)
  2. ↑ 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.  605 (English).
  3. ↑ Webmineral - Bazzite (English)
  4. ↑ a b c Bazzite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 75  kB ; accessed on June 15, 2018]).
  5. ↑ Mindat - Bazzite (English)
  6. ↑ Marco E. Ciriotti, Lorenza Fascio, Marco Pasero: Italian Type Minerals . 1st edition. Edizioni Plus - Università di Pisa, Pisa 2009, ISBN 978-88-8492-592-3 , p. 47 .
  7. ↑ Mindat - Number of locations for Bazzit (English)
  8. ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Dörfler Natur ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 224 .
  9. ↑ Find location list for Bazzit in the Mineralienatlas and in Mindat