Tellurite

Tellurite (deprecated Tellurocker ) is a rarely occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the composition of β - TeO2, is so chemically seen a β - tellurium dioxide.

Tellurite usually develops transparent crystals with acicular to prismatic habit of about two centimeters in size, but also brush-like aggregates or crusty coating of white, yellowish-white or straw to honey yellow color with white stroke color. Uninjured crystal faces fresh samples exhibit a weak diamond shine.

With a Mohs hardness of 2 tellurite is one of the soft minerals, which can be similar to the reference mineral gypsum scratched with a fingernail.

Special Features

Tellurite is practically insoluble in water, but he can conditionally be dissolved in strong acids such as hydrochloric or nitric acid, or in strong bases such as sodium hydroxide by the amphoteric character of the Te ( IV) ion. The corresponding chemical reaction equations can be found at → tellurium dioxide.

Etymology and history

The mineral was named after its main chemical component of the tellurium. The root word can be traced back to the Latin word for earth Tellus.

Was first discovered tellurite in the pit " Fata Baii " ( Facebanya, Faczebaja ) at Zlatna in Alba county in Romania and described in 1842 by William Petz, of the mineral along with native tellurium in some samples in the form of small balls of fine-grained microstructure and yellowish-white found in greyish 's playing color, he. due to the chemical reactions before the blowpipe, identified in the open tube and coal as tellurous acid

Its up today valid name tellurite received the mineral in 1845 by Wilhelm Ritter von Haidinger.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz tellurite belonged to the mineral class of " oxides, hydroxides, " and then to the Department of " Oxides with metal: oxygen = 1:2 ", where he along with brookite, Carmichaelit, Scrutinyi Srilankit and formed a group.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz 's Mineral classification assigns the tellurite also in the class of " oxides ( hydroxides, vanadates, arsenides, antimonides, Bismuthide, Suldide, selenides, tellurides, iodides ) " and in the department of the oxides with a metal -oxygen ratio of 1:2. This department is also further subdivided by the structural configuration so that the mineral according to its construction in the subdivision " with medium-sized cations; can be found with various polyhedra ", where it's the only mineral of the group 04.DE.20.

The mainly common in English-speaking classification of minerals according to Dana assigns the tellurite in the class of " oxides ", there, however, in the department of the " Simple oxides with a cation charge of 4 ( AO2 ) " a. Here tellurite can be found in the subclass 04.04.06.01.

Modifications and varieties

Tellurium dioxide occurs in nature in two different minerals before: paratellurite ( α - TeO 2, tetragonal) and tellurite ( β - TeO2, orthorhombic ). Both modifications are structurally very similar. One, albeit uncertain, distinguishing feature is its color. While tellurite often has a yellow color, paratellurite is almost always colorless. A precise distinction between these two forms is only possible by a crystal structure analysis.

Education and Locations

Tellurite occurs in the oxidation zone of ore deposits. It is associated with other tellurium minerals such as native tellurium or Emmonsite.

Noteworthy due to exceptional Telluritfunde include the " Kawazu mine " in Shimoda and Susaki mine in Japan, where crystals to about apparent wear a centimeter in length. Well -formed crystals were also found in the " Moctezuma Mine" in Mexico

Other localities lie among others in Chile, China, France, Canada, Myanmar, Poland, Russia, Czech Republic, Hungary, and the United States of America (USA).

Crystal structure

Tellurite crystallizes in the orthorhombic space group Pbca ( Raumgruppen-Nr. 61) with the lattice parameters a = 12.03 Å; b = 5.46 Å; c = 5.61 Å, and eight formula units per unit cell.