UDC 549:291,33
LBC 86.41:26.31
  K.305

RUS language
RUS
 

Stone, minerals and semiprecious of the world stone
Oxide and hydrooxide: Blomstrandite, Betafite, Mendelyeevite -->rus

   Diagnostic cart.

   (U, Ca)2 (Ti, Nb, Ta)2 O6(O, OH, F)
   Crystal structure cube
   Hardness on the Mohs scale 3-5,5
   Specific unit weight mass 4,1
   Fracture, break padman
   Colors black, yellow, gold, brown
   Glance (glitter, glare) metallic

   Crystals of this radio-active mineral mostly octahedral; sometimes arrive at imposings sizes (to 10 sm is in a diameter). Much more frequent there are dense the masses. Colors of betafite, not exposed to weathering, black. But under act of the superficial weathering he can pass (mainly in material from tropics, for example, from Madagascar) in brown-yellow, gold. Colors brown, greenish-brown, yellow, gold, green, darkly-brown, greyish-black to black, very often painted unevenly.

   Outsides of crystals are mat often, covered the greyish-yellow triturate products of change. Transparent or opaque (darkly-painted). Crystals, usually shallow, sometimes to 15 sm and more, also the rounded grains and large excretions weighing more than 6 kg Crystals of octahedral type (similar to the crystals of chalcolamprite and microlite), rarer dodecahedral, and also tetragon-trypanosomiasis type. Quite often crystals have a maldevelopment: substantially flattened to on (110) (develop on the plates of mica) or extended along one of axes of 4th or 3th order; rarely flattened to on (100). Mutually-parallel joint, junction of crystals is ordinary. Twins were not observed.

   Diagnostic indication.

   An external type, distinctly isometric, allows to distinguish Blomstrandite, Betafite from most rare minerals. Grains poorly melt flow fuse on edges, become black. So much radio-active; sometimes radio-activity differently shows up in the separate areas of crystals. It is impossible to keep in home collections.

   Origin provenance genesis.

   This rare mineral is typical for pegmatites, where he is in an association with other difficult oxides, such as fergusonite and Evksenite.

   Deposit minefield mine and use.

   Locations are most known on Madagascar, in an area around Betafo and Ampangabe. The best crystals act from there, but always bearings tracks of superficial changes. Fresh material takes a place from Norway (Tangen), Russia (a lake Baykal) and mainly Canada (province of Ontario). The beautiful black crystals of cuboctahedron type act from there. Blomstrandite, Betafite is used in industry for extraction of radio-active elements, included in his composition.


Blomstrandite, Betafite. Antanifuci, Madagascar. A photo: © A.A. Evseev.


Blomstrandite, Betafite. Antanifuci, Madagascar. A photo: © A.A. Evseev.