Vesuvianite
| Vesuvianite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | (Ca, Na) 19 (Al, Mg, Fe) 13 (SiO 4 ) 10 (Si 2 O 7 ) 4 (OH, F, O) 10 |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.BG.35 ( 8th edition : VIII / C.26) 58.02.04.01 |
| Similar minerals | Demantoid, diopside, epidot, hyacinth, peridot, sinhalite |
| Crystallographic Data | |
| Crystal system | tetragonal |
| Crystal class ; symbol | ditetragonal-dipyramidal; 4 / m 2 / m 2 / m |
| Space group | P 4 / nnc (No. 126) |
| Lattice parameters | a = 15.678 Å ; c = 11.828 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 6 to 7 |
| Density (g / cm 3 ) | 3.32 to 3.47 |
| Cleavage | indistinct |
| Break ; Tenacity | uneven to mussel-like, splintery |
| colour | green, yellow, light blue, violet, brown, colorless |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, fat gloss, matt |
| Crystal optics | |
| Refractive indices |
n ω = 1.703 to 1.752 n ε = 1.700 to 1.746 |
| Birefringence | δ = 0.003 to 0.006 |
| Optical character | uniaxial negative |
| Pleochroism | weak |
Vesuvianite (formerly Vesuvian for short ), also called Idokras or Jewreinowit , is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the tetragonal crystal system with the chemical composition (Ca, Na) 19 (Al, Mg, Fe) 13 (SiO 4 ) 10 (Si 2 O 7 ) 4 (OH, F, O) 10 and develops short, prismatic to columnar or tabular crystals , but also radial, granular, massive aggregates in green, yellow, light blue, purple or brown color. Colorless crystals are also known.
Etymology and history
Vesuvianite was first recognized as a separate mineral in 1795 by Abraham Gottlob Werner . He named it after the only known place of discovery at the time, Vesuvius in Italy , which is therefore also considered a type locality . Martin Heinrich Klaproth carried out the first precise chemical analysis . He also recognized the agreement with one of Erik Laxmann 1790 in Siberia found and Hyacinth (a zirconium -Varietät) held mineral sample. A second name is Idokras (Greek for "mixed form") as a reference to its mixed crystal forms.
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the Vesuvianite belonged to the general department of the “ group silicates (sorosilicates)”, where he named the “Vesuvianite group” with the system no. VIII / C.26 and the other members Flurvesuvianit , Manganvesuvianit and Wiluit .
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 Vesuvianite in the category of “group silicates (sorosilicates)”. However, this is more precisely subdivided according to the type of silicate complexes occurring in the compound and the coordination of the cations involved , so that the mineral is classified according to its composition in the subdivision “Group silicates with mixed SiO 4 and Si 2 O 7 groups; Cations in octahedral [6] and greater coordination ”can be found, where he also has the“ Vesuvianite group ”with the system no. 9.BG.35 .
The systematics of minerals according to Dana , which is predominantly used in the English-speaking area , also assigns Vesuvianite to the group of group silicates, but there in the subdivision of “group silicates with insular, mixed, individual and larger tetrahedral groups and cations in [6] and higher coordination; Single and double groups (n = 1.2) ”. Here, however, he can also be found as the namesake of the Vesuvianite group .
Crystal structure
Vesuvianite crystallizes tetragonally in the space group P 4 / nnc (space group no. 126) with the lattice parameters a = 15.678 Å and c = 11.828 Å as well as two formula units per unit cell .
properties
Due to its changing chemical composition, Vesuvianite shows great fluctuations in its physical properties. Weak pleochroism is also occasionally observed, which varies between yellow-green and yellow-brown in green crystals, between yellow and almost colorless in yellow crystals, and between yellow-brown and light brown in brown crystals.
Modifications and varieties
- Californit - green, often erroneously as Vesuvian- Jade referred
- Cyprin - sky blue variety from Norway
- Duparcit - a potassium and iron-rich variety from Morocco, named after Louis Duparc
- Egeran - brownish stalky variety that was already valued as a mineral by Johann Wolfgang von Goethe .
Education and Locations
(size: 7.0 cm × 5.5 cm × 2.7 cm)
Vesuvianite forms either metamorphically or hydrothermally in calcium-rich rocks such as skarn , marble or rodingite . In rare cases, Vesuvianite is also formed in alkaline, igneous rocks . Accompanying minerals include grossular , wollastonite and diopside .
So far (as of 2009) Vesuviant has been found at 960 sites worldwide, including Monzoni in Italy , Asbestos / Quebec in Canada , Hazlov in the Czech Republic , Crestmore / California and Franklin / New Jersey in the USA
Use as a gem stone
Since Vesuvianite is a mineral of medium hardness and low tendency to split, it is often used as a gemstone . Clear crystals are given a facet cut , cloudy varieties are more like a cabochon cut or are made into tumbled stones.
Because of its color, Vesuvianite can be confused with demantoid , diopside , epidote , hyacinth , peridot or sinhalite .
See also
literature
- Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer Verlag, Berlin a. a. 2005, ISBN 3-540-23812-3 , pp. 88 .
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 217 ( Dörfler Natur ).
- Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th, revised and expanded edition. BLV Verlags-GmbH, Munich a. a. 2002, ISBN 3-405-16332-3 , pp. 202 .
Web links
- Mineral Atlas: Vesuvianite (Wiki)
Individual evidence
- ↑ a b c Webmineral - Vesuvianite (English)
- ↑ a b c American Mineralogist Crystal Structure Database - Vesuvianite (English, 2007)
- ↑ a b c Mindat - Vesuvianite (English)
- ↑ IMA / CNMNC List of Mineral Names - Fluorvesuvianite (English; PDF 1.8 MB; p. 298)
- ↑ Martin Heinrich Klaproth: Investigation of the Vesuvians. In: Contributions to the chemical knowledge [ sic ] of the mineral bodies. Volume 2, 1797, pp. 27–38 ( limited preview in Google book search).
- ↑ LJ Spencer: Thirteenth list of new mineral names In: Mineralogical Magazine Volume 23, 1934, pp. 624–640 ( PDF 725.8 kB ( Memento of the original from February 25, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this note. )
- ↑ The Mineralogical Record: Glossary of Obsolete Mineral Names - D (PDF 193.6 kB; p. 20)
- ↑ Johannes Baier: Goethe and the Egeran von Haslau (Hazlov; Czech Republic) - Z. geol. Wiss., 41/42, 115-122; Berlin, 2013/14.
