Tellurite
| Tellurite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | β-TeO 2 |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
04.DE.20 ( 8th edition : IV / D.15) 04.04.06.01 |
| Similar minerals | dimorphic with paratellurite |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Room group (no.) | Pbca (No. 61) |
| Lattice parameters | a = 12.03 Å ; b = 5.46 Å; c = 5.61 Å |
| Formula units | Z = 8 |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | measured: 5.90 (2); calculated: [5.75] |
| Cleavage | completely after {010} |
| colour | white, yellowish white, straw yellow to honey yellow |
| Line color | White |
| transparency | transparent to opaque |
| shine | Diamond luster |
| Crystal optics | |
| Refractive indices |
n α = 2.00 n β = 2.18 n γ = 2.35 |
| Birefringence | δ = 0.350 |
| Optical character | biaxial negative |
| Other properties | |
| Chemical behavior | soluble in strong acids; soluble in strong bases |
| Special features | melts into a red ball in front of the soldering tube |
Tellurite (outdated tellurium ocher ) is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the composition β-TeO 2 , so it is chemically a β-tellurium dioxide .
Tellurite usually develops transparent crystals with a needle-like to prismatic habit of about two centimeters in size, but also cluster-shaped aggregates or crusty coatings of white, yellowish-white or straw to honey-yellow in color with white streak color . Unharmed crystal surfaces of fresh samples have a weak diamond luster .
With a Mohs hardness of 2, tellurite is one of the soft minerals that, like the reference mineral plaster, can be scratched with the fingernail.
Special properties
Tellurite is practically insoluble in water, but due to the amphoteric character of the Te (IV) ion it can be dissolved in strong acids such as hydrochloric or nitric acid or in strong bases such as sodium hydroxide . The corresponding chemical reaction equations can be found under → Tellurium dioxide .
Etymology and history
The mineral was named after its main chemical component, tellurium . The root of the word can be traced back to the Latin word tellus for earth.
Tellurite was first discovered in the "Fata Baii" mine ( Facebanya , Faczebaja ) near Zlatna in the Alba district in Romania and described in 1842 by Wilhelm Petz , who found the mineral together with solid tellurium in some samples in the form of small spheres with a fine-fiber structure and yellowish-white, in the grayish playful color, which he identified as telluric acid based on the chemical reactions in front of the soldering tube , in the open tube and on carbon .
The mineral was given its name tellurite, which is still valid today, in 1845 from Wilhelm Ritter von Haidinger .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz, tellurite belonged to the mineral class of "oxides, hydroxides" and there to the department of "oxides with metal: oxygen = 1: 2", where together with brookite , carmichaelite , Scrutinyi and Srilankit formed a group.
The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also assigns tellurite to the class of "oxides (hydroxides, vanadates, arsenides, antimonides, bismuthides, suldides, selenides, tellurides, iodides)" and in the division of oxides with a metal-to-oxygen ratio of 1: 2. This department is further subdivided according to the structural structure, so that the mineral according to its structure in the subdivision “with medium-sized cations; with different polyhedra ”is to be found, where it is the only mineral of group 04.DE.20.
The systematics of minerals according to Dana, which is mainly used in the English-speaking world, assigns tellurite to the class of "oxides", but there in the department of "simple oxides with a cation charge of 4+ (AO 2 )". Tellurite can be found here in the subclass 04/04/06/01.
Modifications and varieties
Tellurium dioxide occurs naturally in two different minerals: paratellurite (α-TeO 2 , tetragonal) and tellurite (β-TeO 2 , orthorhombic). Both modifications are structurally very similar. One, albeit uncertain, distinguishing feature is their color. While tellurite is often yellow in color, paratellurite is practically always colorless. A precise distinction between these two modifications is only possible through a crystal structure analysis.
Education and Locations
Tellurite occurs in the oxidation zone of ore deposits. It is associated with other tellurium-containing minerals such as native tellurium or emmonsite .
As a rare mineral formation, tellurite could so far (status: 2011) only be detected at a few sites. About 45 sites are known to be known.
The "Kawazu Mine" near Shimoda and the Susaki Mine in Japan, where crystals up to about one centimeter in length came to light, are worth mentioning due to the extraordinary tellurite finds. Well-formed crystals were also found in the “ Moctezuma Mine” in Mexico.
Other locations are in Chile, China, France, Canada, Myanmar, Poland, Russia, the Czech Republic, Hungary, and the United States of America (USA).
Crystal structure
Tellurite crystallizes orthorhombically in the space group Pbca (space group no. 61) with the lattice parameters a = 12.03 Å ; b = 5.46 Å; c = 5.61 Å, as well as 8 formula units per unit cell .
See also
Individual evidence
- ↑ Webmineral - Tellurite (English)
- ^ A b c 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. 215 .
- ↑ Handbook of Mineralogy - Tellurite (English, PDF 69 kB)
- ↑ a b c Tellurite at mindat.org (engl.)
- ^ W. Haidinger: Second class: Geogenide. II. Order. Barytes. VIII. Antimony Baryte. Tellurite , in: Handbook of Determining Mineralogy , Bei Braumüller and Seidel, Vienna 1845, pp. 499–506 ( PDF 512 kB )
- ↑ Mindat - Number of sites for tellurite
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 104 ( Dörfler Natur ).
literature
- Wilhelm Petz : Decomposition of some Transylvanian tellurium ores , in: Annalen der Physik ( Poggendorfs Annalen 1842), Volume 133, Edition 11, pp. 467–478
- Aristides Brezina : About the crystal form of Tellurii (PDF file; 1.6 MB)
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, Stuttgart 1978, ISBN 3-432-82986-8 , p. 539 .
