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PhotosFizélyite - Herja Mine, Chiuzbaia, Baia Mare, Maramureș Co., Romania
12th Jun 2012 00:50 UTCRob Woodside 🌟 Manager
12th Jun 2012 01:37 UTCReiner Mielke Expert
Are all of these fuzzy Fizelyites pseudos? I've seen some for sale which claim they are jamesonite/boulangerite on Fizelyite.
12th Jun 2012 06:40 UTCJean-Francois Carpentier Expert
I have a specimen which does much resemble that of Peter Haas (http://www.mindat.org/photo-31746.html)
In my case, some of the prismatic crystals in the radial fans (to 15 mm) of "Fizelyite" were indeed Fizleyite fully coated by felted powdery Boulangerite / Plumosite (no Jamesonite) and Semseyite (both species confirmed by SEM-EDX). In other crystals of the fans, it looked that the pseudomorphosis (?) to Boulangerite/Semseyite was complete, as no more Fizleyite was detected. There was additional small Freibergite crystals on Sphalerite ore.
jf
12th Jun 2012 18:44 UTCRob Woodside 🌟 Manager
Apparently this material was the last gasp of Herja and came out just before it closed. The fuzzyness is a sure sign of pseudomorphosis and JF's report is the first I've heard of a partial pseudo. Looking at Peter's photo:
There's a broken xl on the lower right in the fan that looks like the partial pseudo that JF describes. Historically (Dana 7) the fizelyite from Herja were unterminated lathes. Semseyite which always? was associated was more tabular with equant arrow like terminations or cockscomb growths. Historic specimens had no fuzz and the fizelyite was greyer than the black semseyite. The fan in Peter's photo is reminiscent of a semseyite cockscomb but the xls are longer like fizelyite. The Van Silver terminated Fizelyites are not so equant with one of the terminal faces much larger. So possibly Fizelyite and Semseyite came in at a low temperature and a higher temperature later event brought in the tetrahedrite and caused the pseudomorphosis to Plumosite and? Semseyite. JF, was there semseyite in the fuzz on Fizelyite. I'm asking if the semseyite was an original mineral or part of the pseudomorph? Plumosite is a well chosen name as some of it was Boulangerite and some Jamesonite and that seems the case here.
Freibergite has had a sad history of being an Argentian Tetrahedrite (Dana 7) to a full species status today. Most older labelled Friebergites are tetrahedrites with a bit of Ag. Over 20 years ago when I was looking at this I remember the figure of merit being 28% by weight Ag. (The Van Silver Tetrahedrites came in at 26% and have red internal lights like Binnite). Since then there has been an almost pure Ag tetrahedrite from Russia. There are a couple of metal sites in the Tetrahedrite structure, but I think they have been lumped to define the current Tetrahedrite nomenclature. What is the wt % of Ag needed these days for real Freibergite?
12th Jun 2012 19:41 UTCNicu Pascanu Expert
Thanks Rob for this warning. Sure, the problem can not be generalized. It might say that these partial / total pseudomorphosis depend on the density of mineralization solutions, temperature etc. Also that individual crystals do not seem ''prone'' to these transformations. On the other hand, the Fizelyite radial aggregates seem to be affected. Specimen ID 427298, 427296 (n. 493 ), self collected and analized much later show no sign of change, aggregates are strongly deformed, poorly coverage, association with small Baryte and Calcite as well. Certainly, another occurrence. About the specimen discussed, that's strange the thiny external cortex Boulangerite between radial Fizelyite.
About ''Jamesonite included calcites from Herja''-certainly the Herja black calcites appearance, with their slightly curved shapes, as a consequence of jamesonite rich solution formation. Many specimens were identified and confirmed as Virgil Ghiurcă (2005) studies.
Regards,
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