Dumortierite
| Dumortierite | |
|---|---|
 |
|
| General and classification | |
| chemical formula |
|
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.AJ.10 ( 8th edition : VIII / B.31) 54.01.02.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Room group (no.) | Pmcn (No. 62) |
| Lattice parameters | a = 11.83 Å ; b = 20.24 Å; c = 4.70 Å |
| Formula units | Z = 4 |
| Twinning | Triplets after {110} |
| Physical Properties | |
| Mohs hardness | 7 to 8.5 |
| Density (g / cm 3 ) | measured: 3.21 to 3.41; calculated: 3.45 |
| Cleavage | clear after {100}, indistinct after {110}; Secretions after {001} |
| Break ; Tenacity | uneven |
| colour | blue, greenish-blue, violet, red-violet to brown-violet |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, weak silky gloss, matt |
| Crystal optics | |
| Refractive indices |
n α = 1.659 to 1.678 n β = 1.684 to 1.691 n γ = 1.686 to 1.692 |
| Birefringence | δ = 0.027 |
| Optical character | biaxial negative |
| Axis angle | 2V = 20 to 52 ° (measured); 30 ° (calculated) |
| Pleochroism | strong: X = dark blue or violet Y = yellow to red-violet or almost colorless Z = colorless or very light blue |
Dumortierite is a seldom occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the idealized composition Al 6.5–7 [(O, OH) 3 | BO 3 | (SiO 4 ) 3 ], so it is chemically an aluminum borosilicate with additional oxygen or hydroxide ions . Structurally, Dumortierite belongs to the island silicates .
In natural dumortierite, a small proportion of the aluminum is often replaced ( substituted ) by magnesium (Mg) or iron (Fe ). In addition, this structural space is not always fully occupied (□), which is generally expressed by the formula Al 6 (Al, Mg, Fe 3+ , □) [(O, OH) 3 | BO 3 | (SiO 4 ) 3 ] .
The mineral is usually found in the form of parallel-fiber or radial-rayed crystals and aggregates of blue, greenish-blue, violet or red-violet to brown-violet color with white streak color . Visible crystal surfaces have a glass-like luster , whereas dumortierite is matt in coarse aggregate forms .
The well-known natural stone variety Azul Do Macaubas contains about 15% Dumortierite, which is the reason for the strong blue color of the stone.
Special properties
Due to intense annealing , dumortierite changes into the mineral mullite , releasing water (H 2 O) and boron trioxide (B 2 O 3 ) .
Etymology and history
Dumortierite was first discovered in the "Ducarre" quarry in Chaponost in the French department of Rhône and described in 1881 by MF Gonnard, who named the mineral after the French paleontologist Eugène Dumortier (1801–1876).
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the dumortierite belonged to the department of “island silicates with non-tetrahedral anions (Neso subsilicates)”, where together with grandidierite it forms the “dumortierite-grandidierite group” with the system No. VIII / B.31 and the other members Boralsilit , Harkerit , Holtit , Kornerupin , Magnesiodumortierit , Ominelit , Prismatin and Werdingit .
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 dumortierite in the category of " island silicates (nesosilicates)". This is, however, further subdivided according to the possible presence of further anions and the coordination number of the cations involved , so that the mineral is classified according to its composition in the subsection " Island silicates with BO 3 triangles and / or B [4] , Be [4] tetrahedra, corner-dividing with SiO 4 ”is to be found, where it forms the unnamed group 9.AJ.10 together with holtite and magnesiodumortierite .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Dumortierite to the class of "Silicates and Germanates" and there in the department and subdivision of the same name of "Island silicates: borosilicates and some beryllosilicates with (BO 3 )". Here he is the namesake of the " Dumortieritgruppe " with the system no. 54.01.02 and the only other member to find magnesiodumortierite.
Education and Locations
Dumortierite forms in aluminum-rich, regionally metamorphosed , granitic pegmatites , migmatites or gneisses . The accompanying minerals include andalusite , cordierite , kyanite , muscovite , quartz , rutile , sillimanite , scapolite , topaz and tourmaline .
As a rather rare mineral formation, dumortierite can sometimes be abundant at various sites, but overall it is not very common. So far (as of 2013) around 200 sites are known to be known. In addition to its type locality , the “Ducarre” quarry, the mineral could also be found in France in the municipality of Saint-Laurent-de-Chamousset, which also belongs to the Rhône department, and near Rouquié (municipality of Lamontélarié ) in the Tarn department .
In Germany, dumortierite appeared at Egerten in Baden-Württemberg, Drachselsried and Ahornberg in Bavaria, Rockeskyll (Eifel) in Rhineland-Palatinate, and in the Ratssteinbruch near Hartmannsdorf (near Chemnitz) and Waldheim in Saxony.
In Austria the mineral could so far at Arlinggraben near Kötsch ( municipality Wolfsberg ), at Ladinger Spitz and at Bad St. Leonhard in Lavanttal in the Carinthian Saualpe ; near Meidling (municipality of Paudorf) , on Unterkienstock near Rossatz-Arnsdorf and at Zwettler Leiten near Felling ( municipality of Gföhl ), Ebersdorf (municipality of Leiben) and near Amstall in Lower Austria as well as on Kuppergrund near Osterwitz , on Wildbachgraben and near Schwanberg in Styria .
In Switzerland, known previously only from Dumortierite Forno Glacier in the canton of Grisons, from the Pontetal and Crodolotal near Brissago and from Castione TI in the canton of Ticino.
Other locations are in the Antarctic, Australia, Austria, Bolivia, Botswana, Brazil, Bulgaria, Chile, Finland, India, Italy, Japan, Canada, Madagascar, Mozambique, Namibia, New Zealand, Norway, Peru, Poland, Russia, Sweden , Switzerland, Slovakia, South Africa, South Korea, the Czech Republic, the Ukraine, the United Kingdom (England) and the United States of America (Alaska, Arizona, California, Main, Montana, Nevada, New Mexico, New York, North Carolina, Pennsylvania, Utah, Washington).
Crystal structure
Dumortierite crystallizes orthorhombically in the space group Pmcn (space group no. 62) with the lattice parameters a = 11.83 Å ; b = 20.24 Å and c = 4.70 Å and 4 formula units per unit cell .
use
As a gem
Similar to sodalite and lapis lazuli , dumortierite is mainly used as a gemstone . Cabochon and other smooth cuts are preferred for dense aggregate shapes, and various facet cuts are preferred for crystals. In addition, aggregate forms are also processed into various craft objects such as animal sculptures.
Due to its similarity in color to sodalite and lapis lazuli as well as in crystal form with azurite , blue quartz there is a certain risk of confusion with these minerals. Blue quartz with inclusions of dumortierite is more precisely referred to as dumortierite quartz or dumortierite quartz .
As a raw material
Occasionally, dumortierite is used as a ceramic raw material for insulators and laboratory equipment.
See also
literature
- MF Gonnard: Note sur l´existance d´une espèce minérale nouvelle, la dumortiérite dans le gneiss de Beaunan, au-dessus des anciens aqueducs galloromains de la vallée de l´Izeron (Rhône) , In: Bulletin de la Société Minéralogique de France , Volume 4 (1881), pp. 2–5 ( PDF 224.2 kB )
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 686 (first edition: 1891).
- Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 703 .
- Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 495 .
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 209 ( Dörfler Natur ).
Web links
- Mineral Atlas: Dumortierite (Wiki)
- Database-of-Raman-spectroscopy - Dumortierite
- American-Mineralogist-Crystal-Structure-Database - Dumortierite
- realgems.org - Dumortierite (with picture examples of cut Dumortierite)
Individual evidence
- ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
- ↑ 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. 561 .
- ↑ Webmineral - Dumortierite
- ↑ a b Dumortierite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 74.3 kB )
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 209 ( Dörfler Natur ).
- ↑ a b c Mindat - Dumortierite
- ↑ Friedrich Müller: Geology , Ebener Verlag, 2005, ISBN 3-87188-122-8 , p. 158
- ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 703 .
- ↑ Mindat - Number of localities for Dumortierite
- ↑ Find location list for Dumortierite at the Mineralienatlas and at Mindat
- ^ 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 et al. 2002, ISBN 3-405-16332-3 , p. 198 .
- ↑ Bernhard brother embellished stones . Neue Erde Verlag, 2005, ISBN 3-89060-025-5 , p. 53 .
- ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 495 .