Marthozite

Marthozit is a very rarely occurring uranium mineral from the mineral class of " oxides and hydroxides " (including V [ 5,6] vanadates, Arsenites, Antimonite, Bismutite, sulfites, Selenite, Tellurite and Iodate ). It crystallizes in the orthorhombic crystal system with the chemical composition Cu (UO2 ) 3 ( SeO3 ) 2O2 · 8H2O, that is a hydrous copper uranyl selenite.

Marthozit often developed yellow-green, pyramidal crystals and yellow aggregates.

Special Features

The mineral is radioactive due to its uranium content of up to 54.78 %. Taking into account the proportions of radioactive elements in the idealized empirical formula and the Folgezerfälle the natural decay series is for the mineral has a specific activity of about 98 kBq / g (compared to natural potassium 0.0312 kBq / g). The quoted value can vary significantly depending on the mineral content and composition of the stages are also selective on or depletions of radioactive decay products possible and changing the activity.

Etymology and history

( Democratic Republic of Congo today ) discovered and described in 1969 by Fabien Cesbron, Robert Oosterbosch and Roland Pierrot, which named the mineral after the French mineralogist Aime Marthoz ( 1864-1962 ) was Marthozit first time a mineral sample from the Musonoi mine in Katanga.

The initially specified by the Erstbeschreibern sum formula Cu (UO2 ) 3 ( SeO3 ) 3 ( OH) 2.7 H2O could be corrected 3 ( SeO3 ) 2O2 · 8H2O in 2001 by single-crystal structure to Cu ( UO2).

The type of mineral is located in the Natural History Museum in Paris.

Classification

The dated 8th edition of Strunz lists the Marthozit under the " Uranylselenite with modules [ UO2 ] 2 to [ SeO3 ] 2 - " with the system no. IV/K.11 together with Demesmaekerit, Derriksit, Guilleminit, Haynesit, Larisait and Piretit.

The 9th, completely revised edition of Strunz lists the Marthozit in the Department J " Selenites with additional anions, with H2O" as the only representative of the group 4.JJ.05.

The commonly used in English-speaking classification of minerals according to Dana assigns the Marthozit under the Selenite - Tellurite - sulfites within the sulphates, chromates and molybdates with the system no. 53.03.03.01 one.

Education and Locations

Marthozit forms as a secondary uranium mineral in the oxidation zone of selenium-rich hydrothermal uranium ores. It is found associated with digenite, Demesmaekerit, Denningit, Guilleminit. In addition to the type locality in the Kasolo mine at Kolwezi there is Marthozit world only in " La Creusa U prospect " Marécottes in the canton of Valais in Switzerland as well as possibly. Moldava in Dubi in the Czech Republic

Crystal structure

Marthozit crystallizes in the monoclinic space group Pbn21 ( Raumgruppen-Nr. 33) with the lattice parameters a = 6.9879 Å; b = 16.4537 Å; c = 17.2229 Å and four formula units per unit cell.

The crystal structure has three different Marthozit uranyl units, of which a hexagonal bipyramidal, the other two are pentagonal- bipyramidal surrounded by oxygen atoms. The selenite units form trigonal pyramids with the selenium atom as a point. This creates layers of uranyl cations and selenite anions, which are bridged to each other by the Cu2 ions. The copper ions but only coordinate pentagonal bipyramidal Uranyleinheiten. The copper itself is surrounded by four units of water of crystallization, so that it is octahedrally surrounded by six oxygen atoms.

Layer structure of Marthozit in the direction of the crystallographic b- axis ( __ U __ O __ Se __ Cu ( water molecules removed for clarity ) )

Metamarthozit

Both Cesbron, Oosterbosch and Pierrot as well as Cooper and Hawthorn report a meta- form of Marthozit. The work of the latter authors indicates a molecular formula of Cu (UO2 ) 3 ( SeO3 ) 2O2 · 6H2O for Metamarthozit. He also crystallized orthorhombic with similar cell dimensions, with only the b- axis is shortened to 15.8 Å.

Precautions

Due to the strong radioactivity of the mineral should mineral samples from Marthozit in a dust - and radiation- tight containers are mainly but never kept in living, sleeping and working areas. Should be definitely prevented and the safety of direct body contact and worn when handling the mineral mask and gloves also because of the high toxicity and radioactivity of uranyl inclusion in the body ( incorporation, ingestion).