Betafite

Betafit (also Blomstrandit, Mendeleyevit or Samiresit ) is a rarely occurring mineral from the mineral class of oxides and hydroxides. It crystallizes in a cubic crystal system having a chemical composition (Ca, U) 2 (Ti, Nb, Ta ) 2 ( O, OH ) 7 and usually develops octahedral crystals, but also bulky mineral aggregates and crusty coatings of initially yellow, red or greenish brown in color, which varies over time by metamikte destruction in continuous brown to black.

Special Features

Is Betafit by its highly radioactive uranium content with a specific activity of about 31 kBq / g (compared to natural potassium 31.2 Bq / g).

Etymology and history

Was first described in 1912 by Antoine Lacroix Betafit. He named the mineral after its type locality Betafo Madagascar.

Classification

In the old classification of minerals according to Strunz (8th Edition) Betafit still belongs to the Department of oxides with the molar ratio of metal: oxygen = 2: 3

After the mineral was firstly redefined in its chemical composition and on the other Strunz'sche Mineral classification in the 9th edition underwent a reorganization and accurate subdivision, the mineral is now in the subdivision of " oxides with the molar ratio of metal: oxygen = 1: 2 and comparable with large (± medium-sized ) cations; Layers of edge-sharing octahedra. "

The classification of minerals according to Dana sorted the Betafit also in the class of oxides and hydroxides and there in the subdivision of multiple oxides with Nb, Ta and Ti with the general formula A2 ( B2O6 ) ( O, OH, F). The mineral is there named after a subgroup of the Pyrochlorgruppe.

Education and Locations

Betafit forms predominantly primarily in granitic pegmatites and rarely in carbonatites. Accompanying minerals include allanite, beryl, biotite, magnetite, microcline, quartz, thorite, titanite and zircon.

Large crystals with up to six kilograms of weight can be found at its type locality Betafo Madagascar. Other localities on this island are Fianarantsoa, Mahajanga and Toliara. Worldwide joined Betafit so far (as of 2009) on the following localities to:

South Australia ( Hot Springs area) in Australia; Minas Gerais in Brazil; Jiangxi, Liaoning and Sichuan in China; Kropfmühl (Bavaria) and the Eifel ( Rhineland -Palatinate ) in Germany; Southern Finland; Kitaa in Greenland; Barima - Waini in Guyana; Naples, Viterbo, Lombardy and Piedmont in Italy; at Kribi in Cameroon; Bancroft ( Ontario) ( " Silver Crater Mine" with crystal sizes up to 10 cm) and Québec ( Abitibi, Oka ) in Canada; at Chitipa in Malawi; Oaxaca in Mexico; Zambezia in Mozambique; Kangwŏn -do in North Korea; Aust- Agder and Telemark in Norway; Silesia in Poland; Eastern Siberia and Murmansk Oblast in Russia; Mintaqah ' Asir in Saudi Arabia; Canton of Graubünden in Switzerland; in Banská Bystrica in Slovakia; South Africa; Alai in Tajikistan; Bohemia and Moravia in the Czech Republic; as well as in various regions of the United States.

In Mare Crisium on the Moon mineral samples were brought from Betafit during the Luna - 24 mission.

Crystal structure

Betafit crystallizes in the cubic crystal system in the space group with the lattice parameters a = 10.1579 Å and 10 formula units per unit cell.