Pyrochlore Supergroup var: Betafite (fine crystal)

Item Description

Betafite was named in 1912 after the Betafo District in Madagascar where the crystals were first discovered. It remained a valid species for decades, but it is now defined as a variety of the Pyrochlore Supergroup. The entry on mindat.org reads as follows, "True "Betafite" samples are structurally members of the pyrochlore supergroup. Hogarth (1977) stated that the betafite group has 2Ti ≥ (Nb + Ta), however the formulae of most betafites do not exactly correspond to pyrochlores and that difference has delayed their classification. The result of modern microprobe analyses is that almost all specimens formerly labeled betafite are no longer members of that group. New analyses, including determination of H^2O, OH, and F are necessary to identify the species of a particular sample. The root-name, betafite, was retained for historical reasons." With that said, you will likely still see these crystals labeled as Betafite. This piece is a wonderful example of this old classic material featuring sharp, well-defined octahedral faces with thin dodecahedral modifications on the edges, and a gentle golden-yellow hue. The piece is in great condition on the top / display side, but it's contacted on the back/bottom where it was removed from the pocket wall. Beautiful old classic material, and to find a piece with such smooth and well-formed faces is not terribly common.
From the collection of Vasco Trancoso, a medical doctor and prominent mineral collector from near Lisbon, Portugal (https://www.mindat.org/user-11954.html). He assembled his mineral collection over the course of 60 years, and built a fine worldwide display collection that we recently purchased. This piece is pictured on mindat.org at https://www.mindat.org/photo-189595.html