betafite

betafite

[′bed·ə‚fīt]
(mineralogy)
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At the Main Show, John was selling specimens showing reasonably sharp, dull brown betafite cuboctahedrons to 3 cm; crystal clusters, with or without matrix, to 7 cm were going for $50 to $150.
Sure enough, from the old biotite and uranium workings known as the Silver Crater mine, near Bancroft, he dug out betafite crystals by the dozen, some equaling the best from the 1950's and 1960's for sharpness and general class.
His big betafite from Madagascar--I haven't seen better.
Included were Madagascar rare-earth classics like sharp betafite crystals to 4 cm; well-composed earthy brown sprays of 2-cm euxenite crystals; swarms of loose 1 and 2-cm cubes of lustrous black thorianite; and allanite crystal groups from Madagascar and from Alto Ligonha, Mozambique.
5-cm thorianite crystal, a "reinite" (ferberite pseudomorph after scheelite) from Uganda, and a razor-sharp dodecahedral betafite of about 2 cm.
Associations include betafite, euxenite, monazite and xenotime-(Y) (DSGM, 1974).
Betafite has been reported from the Ile pegmatite, in association with euxenite, allanite and monazite, and from the Ehiale-Namovela-Massive-Horta group in association with euxenite and samarskite (DSGM, 1974).
Solid-solution between pyrochlore and betafite is indicated by the microprobe analyses.
A bismuth-dominant betafite has previously been reported from the Malkhan pegmatites, Transbaikalia (Zagorsky and Peretyazhko, 1992).
Also obtained by exchange from one or several of these localities are many other rare and interesting species such as superb danburite, nosean, afghanite, transparent allanite, tadzhikite-(Ce), green thorite, urano-thorianite, asbecasite, stillwellite-(Ce), transparent brown baddeleyite, tiny red-brown crystals of betafite, very small, dark brown crystals of zirconolite-3T, and beautiful, greenish yellow, transparent crystals of vicanite-Ce.