Billietite

Billietit is a rarely occurring uranium mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the chemical composition of Ba [( UO2) 6 | O4 | (OH ) 6] · 8H2O and usually develops translucent, prismatic and pseudo-hexagonal crystals of yellow-brown to amber- brown color with yellow stroke color. In the crystal surfaces reveals a diamond-like luster. Star-shaped formation formed by drilling units are typical of the mineral. It is chemically considered a hydrated barium Uranyloxid.

Special Features

The mineral is characterized by its uranium content of up to 69.1 wt - classified as very highly radioactive % and has a specific activity of about 123.6 kBq / g (compared to natural potassium 0.0312 kBq / g).

Etymology and history

Billietit was first described in 1947 by the Belgian mineralogist Johannes Franciscus Vaes, who named it in honor of the Belgian mineralogist Louis Valere Billiet ( born February 14, 1903 in Ghent). Billiet was in the French Resistance active, captured on August 10, 1944, and was eventually murdered shortly before the end of the war in a prisoner transport by the SS.

There are two type of minerals, of which one, USA is located at Harvard University in Cambridge, Massachusetts, USA, and another at the National Museum of Natural History, Washington, DC.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Billietit belonged to the mineral class of " oxides and hydroxides " and then to the Department of " uranyl hydroxides and hydrates ", where he and along with Becquerelit, Compreignacit, Masuyit Protasit an independent group formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Billietit also included in the category of " oxides and hydroxides " and there in the department of " Uranyl Hydroxide ." This division, however, is further subdivided according to the presence of other cations, as well as the crystal structure, so that the mineral, according to its composition and structure in the sub-department "With additional cations (K, Ca, Ba, Pb, etc.), mainly UO2 (O OH) 5 pentagonal polyhedra "in the" Becquerelitgruppe " ( System-Nr. 4.GB.10 ) can be found along with the namesake Becquerelit and Protasit.

The classification of minerals according to Dana assigns the Billietit in the class of " oxides and hydroxides ", but there in the department of " uranium and thorium oxides " one. He is also in the " Becquerelitgruppe " with the system no. 05:07:01 along with Compreignacit and Becquerelit within the sub-division of " uranium and thorium oxides with alkali or hydrated Hydroxidkomponenten " to find.

Education and Locations

Billietit can be found as a rare alteration product in the oxidation zone of primary uranium ore deposits. The mineral varies by locality associated with uranophane, Fourmarierit, Rutherfordin, Becquerelit, studtite, Soddyit and Torbernite.

In addition to the type locality in Shinkolobwe Billietit was also found in the Swambo mine. From Germany Billietit among others from the pit Krunkelbach at Menzenschwand, from Wittichen ( pit Sophia ) from the Heubachtal ( pit Anton ) and Oberwolfach ( Grube Clara ) and from mountains in Saxony is known. In Switzerland, it was found in the canton of Valais in Eifischtal and Trient. Other localities are in the Alsace region of France, the uranium deposit Kruth 2 as well as in the region of Languedoc -Roussillon in the Hérault département in Rabejac at Lodève. In Italy it was in Rendena, found in the U.S. in the Delta picks mine in Utah and Australia in the Radium Ridge. Other localities are the Lianshanguan mine in China, Labe dam, Moldava ( Moldavia ) and Slavkovice in the Czech Republic, the Eureka Mine in Spain, as well as the Åsnebo mine in Sweden.

Crystal structure

Billietit crystallizes in the orthorhombic crystal system, space group Pbn21 with the lattice parameters a = 12.07 Å, b = 30.16 Å, c = 7.14 Å and β = 123.36 °, and four formula units per unit cell.

In the crystal structure of the uranium atom has a pentagonal- bipyramidal geometry. This form through the coordination of oxygen atoms on two types of layers of corner-sharing and edge- Uranylpolyeder. The first type corresponds to the layers in the structures of Ianthinit and Wyartit. The second type corresponds to layers in the structures of Protasit, Compreignacit and Becquerelit. These layers alternate along the crystallographic b- axis and are linked by barium atoms. The barium atom is six uranyl oxygen atoms (distances from 2.77 to 2.99 Å ) and four coordinated water molecules (distances from 2.77 to 2.86 Å). This coordination is similar to that of barium in the minerals Guilleminit and Protasit.

Use

Due to the barium content of the Billietits, which occurs as a gap element in nuclear waste, it is suitable as a study object for the oxidation of spent nuclear fuel in groundwater, the incorporation of different radionuclides in hydrated Uranyloxiden and mobility study of radioactive waste.

Precautions

Due to the strong radioactivity of the mineral should mineral samples from Billietit 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).