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General(Meta)torbernite: which species to add to locality?

11th Apr 2018 17:18 UTCEd Clopton 🌟 Expert

A specimen from the Consolidated quarry, Georgetown, Maine has been identified as containing torbernite, which is a new species for the locality. Identification was by SEM, which I understand would not detect the presence or absence of water. It is assumed that torbernite dehydrates to metatorbernite under surface conditions, so the little green scales as they now stand are most likely metatorbernite.

The question is this: Which species should I add to the locality page? Pieces lying around on the surface there most likely have dehydrated, so metatorbernite could be said to occur there. But can we assume that material still in situ (i.e., not yet exposed to the atmosphere) formed as, and probably still is, torbernite? Or might it have formed originally as metatorbernite? Does the presence of (presumed) metatorbernite necessarily indicate that torbernite exists (or existed) there as well?

Bottom line, should I add both to the species list and upload my photos under metatorbernite?

11th Apr 2018 17:40 UTCUwe Kolitsch Manager

Are they transparent or opaque? In the latter case, it's definitely metatorbernite.

> It is assumed that torbernite dehydrates to metatorbernite under surface conditions

Not always - depends on conditions.

11th Apr 2018 19:28 UTCRichard Gunter Expert

The conditions for dehydration in the uranium phosphates/arsenates can change in a few centimeters. I have a sample of Zeunerite/Metazeunerite from Majuba Hill that has perfectly transparent green plates on one side of the 5 cm sample and opaque light green plates on the back of the sample. It may have to do with the amount of oxygen present in the fractures prior to collecting.

11th Apr 2018 22:27 UTCReiner Mielke Expert

It could also have to do with which side was displayed in hot lights or the sun. I can't see what oxygen has to do with dehydration but air circulation would, maybe that is what you meant?

11th Apr 2018 23:36 UTCRichard Gunter Expert

Hi Reiner:

I think this sample was one that John Degenais collected underground so the differences would have come from air circulation.

12th Apr 2018 11:19 UTCUwe Kolitsch Manager

Could be just two different generations (note that cloudi- or opaqueness can also be caused by fluid inclusions).

"Air circulation" basically means you may have slightly different humidities and temperatures.

12th Apr 2018 14:35 UTCEd Clopton 🌟 Expert

The crystals are translucent and a little pearly, but not transparent. Should I just add metatorbernite to the locality page and skip torbernite entirely?

12th Apr 2018 15:25 UTCUwe Kolitsch Manager

Yes.

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