Pyrochlore Supergroup var: Betafite

Item Description

This is good quality and classic example of what used to be labeled as "Betafite" from the Silver Crater Mine in Bancroft, Ontario. It should be noted that for many years, Betafite was a valid species. It was named in 1912 after the Betafo District in Madagascar where the crystals were first discovered. In recent years, the material has been reclassified 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 good sized, sharp, well-defined near "floater" cuboctahedral crystal with a deep golden-brown hue. The piece is in great condition all around, with no major damage, but I can see what looks like either a separation mark or a slight point of attachment on one face, so I'm not going to call it a totally complete "floater". Beautiful old classic material, and to find a piece with such smooth and well-formed faces is not terribly common. I'm told that these specimens were mined in the 1950s, and are certainly regarded as some of the finest examples of "Betafite" ever found.