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Generalschalenblende

15th Dec 2017 21:11 UTCMichel Blondieau

Dear all,

"Schalenblende" is an Zn ore colloform variety known as to contain sphalerite and wurtzite. In the area of Moresnet (Belgium), the mixture of these two species is only accreedited by a really old paper (Noelting, 1887). But no recent paper seems to prove that ! I have analysed by RX diffraction specimens of "schalenblende" from Lontzen (Rabotrath and Erlenbach), a locality just near Moresnet, in Belgium, and no wurtzit was found; only sphalerit ! I suspect that all these "schalenblende" from Belgium don't contain wurtzite at all. But I am perhaps wrong and I would be glad to know if scientific paper have been written on that. Are there any localities worldwide with "schalenblendes" known to show mixtures of sphalerit and wurtzit ? If so, is it really sure ? If necessary, I can do some DRX analyses on some specimens and write a paper about that. Material needed has to be pure but quantity needed is under 1 cm³.

Thank you for all your answers and help.

Michel Blondieau,

Belgium

15th Dec 2017 21:36 UTCHarjo Neutkens Manager

Michel, do you have any good schalenblende specimens from Seilles? If not, I can send you one.

The information I have about the schalenblende specimens from Rohdenhaus, Wülfrath, Germany is that they only contain sphalerite, no wurtzite.

Amicalement,

Harjo

15th Dec 2017 23:23 UTCRichard Gunter Expert

In the Pine Point, Northwest Territories Canada deposits schalenblende: https://www.mindat.org/photo-426533.html has proven to be sphalerite in a paper by Fowler and L'Heureux (1996): Self Organizing Banded Sphalerite and Branching Galena in the Pine Point Deposit, Northwest Territories. Canadian Mineralogist v. 34 pp. 1211-1222. They do thin section work on the sphalerite botryoids and find no conclusive evidence for wurtzite. There are some areas of anisotropic intergrowths but these still appear to be sphalerite.

16th Dec 2017 11:48 UTCMichel Blondieau

Thank you for your replies,

Harjo, I have a lot of schalenblendes from Seilles and I'll do some analyses on them. In your nice mindat page on schalenblende, I read that schalenblende from Poland are usually a mixture of sphalerite and wurtzite. Any paper on that ?

Richard, Thank your for that information. Next week, I'll get that paper. It seems that a lot of new analyses on such material show only sphalerite with no wurtzite. It's what I think too for probably all schalenblende worldwide ! But I'll do analyses ...

Thank again,

Michel

16th Dec 2017 12:40 UTCPaul De Bondt Manager

Schalenblende from Wiesloch doesn't contain wurtzite either.

16th Dec 2017 12:52 UTCAlfredo Petrov Manager

When one talks about "no wurtzite", I think one needs to distinguish between "There never was any wurtzite" and "There used to be some wurtzite but it has now altered to sphalerite". An awful lot of the things in collections called "wurtzite", because they look like wurtzite, used to be wurtzite but are now sphalerite. In the case of schalenblendes, I don't know, I'm just curious.

16th Dec 2017 13:01 UTCErik Vercammen Expert

Is wurtzite part of the definition of schalenblende? or is that layerd (ex)colliform sfalerite +/- wurtzite +/- galena +/- pyrite/marcassite?

16th Dec 2017 13:30 UTCMichel Blondieau

Thanks again for all these replies.

Harjo, do you have a paper for the schalenblende from Wülfrath ?

Paul, I ask the same for the schalenblende from Wiesloch.

Alfredo, it's curious but I have found something about that :

https://pubs.geoscienceworld.org/segweb/economicgeology/article-abstract/87/1/113/20973/mineralogy-paragenesis-and-mineral-zoning-of-the?redirectedFrom=PDF

Erik, I think it's known as layers of sphalerite and layers of wurtzite...

Thanks,

Michel

16th Dec 2017 13:41 UTCPaul De Bondt Manager

Michel,

There is a Lapis number on the subject. Can bring it to Hannut next year.

16th Dec 2017 13:55 UTCAlfredo Petrov Manager

Thanks, Michel! That paper shows that, at least in the Viburnum Trend, the schalenblends used to contain wurtzite, but it has now altered to sphalerite.

I think schalenblende should be defined as its name suggests: "schalen" for the shape, and "blende" for the dominant constituent (sphalerite). What else is in it as subsidiary constituents (wurtzite, marcasite, galena...) is going to vary from locality to locality.

16th Dec 2017 14:51 UTCReiner Mielke Expert

I think the important thing is that schalenblende does not need to contain wurtzite to be schalenblende so wurtzite should not be part of the definition.

16th Dec 2017 15:22 UTCMichel Blondieau

Paul, is it an old issue of Lapis ? Perhaps december 1985 ?

Reiner, I agree with that but the problem I'd like to solve is that one said there are sphalerite and wurtzite in the schalenblende from Moresnet (Belgium) and I don't think so. And to give an answer, I would like to know if there are really worldwide specimens of schalenblende with wurtzite as it's often said.

Thanks,

Michel

16th Dec 2017 15:55 UTCDonald B Peck Expert

Wurtzite was found at Thomaston Dam RR Cut in the 1960s and analyzed at Yale, It and harmatome were the big discoveries there. The wurtzite has/had the typical hexagonal "pagoda" habit. But, I believe that later analyses showed that the wurtzite was really sphalierite. Given the crystal habit, it would seem that it was a conversion.

16th Dec 2017 17:19 UTCChristof Schäfer Manager

Michel,

Ramdohr (Die Erzmineralien und ihre Verwachsungen, 1960) mentions Wurtzite in Schalenblende from Diepenlinchen, Eschbroich, Altenberg, Schmalgraf. Sphalerite replacing Wurtzite is common, wurtzite seems to be rare.

Ramdohr refers to Ehrenberg H. (1931): Der Aufbau der Schalenblende der Aachener Blei-Zink-Lagerstätten……., Neues Jahrbuch Mineralogie, Beilagen Band 64A, pp 397-422

16th Dec 2017 17:53 UTCMichel Blondieau

Donald,

Thanks for that information. Wurtzite seems to be very often converted into sphalerite ! Alfredo already mentionned it .

Christof,

I have specimens from Eschbroich and Schmalgraf and I will do analyses on them. If they only contain sphalerite, it will be difficult to prove that wurtzite has been converted to sphalerite; these schalenblende are colloform ores and don't show any crystals habits ... What were the analyses done by Ehrenberg and others to mention wurtzite in schalenblende ?

Thanks for all your helpfull replies,

Michel

17th Dec 2017 15:55 UTCChristof Schäfer Manager

Michel,

Ramdohr uses optical properties in reflected light for identification and in some cases XRD.

If I understand right he first looked for layers in the Schalenblende that consist of prismatic crystals that have no twinning lamellae (all sphalerite has twinning lamellae). And later in a second step part of such a sample was charakterised with XRD.

17th Dec 2017 16:36 UTCMichel Blondieau

Christof,

Thank you for these informations. First, I will do some researchs in the existing publications and then see how to work.

Do you have Ramdohr's paper ? I am not sure to find it easily here in Belgium but I will do a quick search in the laboratory at the end of next week.

Thanks again,

Michel

17th Dec 2017 17:22 UTCJohn Mason Expert

Hi Michel - here in Central Wales there are banded "blendes" with some very distinctly fibrous layers. If you would like to examine them I can go grab a sample. They are definitely part of the later low-temperature mineralisation.

17th Dec 2017 18:47 UTCHarjo Neutkens Manager

Salut Michel,

I don't have access to a paper on the Rohdenhaus schalenblende, but I'll try to contact the mineralogist who did most of the work for the Mineralienwelt articles about Rohdenhaus.

No information about the Polish ones either. Maybe Tomas from Spirifer has info about them, I'll ask him.

I'll send you a private message because I have a question for you too ;-)

Cheers,

Harjo

17th Dec 2017 21:24 UTCMichel Blondieau

Hi John,

thank you for your post. If you think the specimens from Central Wales could be sphalerite and wurtzite, I am really interested to examine one of them. Thank you for your proposal. With a small sample (really small !) I'd like to obtain too a picture of the specimen and see how the different layers are. For your advice, are there any analyses done on the schalenblendes from that locality or area ?

Salut Harjo,

I surely would be pleased to know much more about the Rohdenhaus schalenblendes and about the polish ones too.

Thanks to all,

Michel

18th Dec 2017 09:28 UTCJohn Mason Expert

Hi Michel,

The later-stage mineralisation is relatively uninvestigated. Most of it is found E and SE of Aberystwyth (south of my postgrad research area). If you can message me contact details I'll send you a small piece.

18th Dec 2017 09:48 UTCMichel Blondieau

Hi John,

Thank you for your proposal.

You can send the specimen at the laboratory at the following address :

BLONDIEAU MICHEL

Laboratoire de Minéralogie, B18

Université de Liège

Allée du 6 août, Sart-Tilman

B-4000 Liège

BELGIUM

Really thanks to help me.

I'll give you results of the analyses.

Michel

18th Dec 2017 10:33 UTCJohn Mason Expert

No probs - expect something in the post early in the new year.

18th Dec 2017 10:40 UTCJohn Mason Expert

From that Economic Geology abstract:

"The presence of rapidly deposited, colloform ZnS and FeS 2 and bladed galena in the central Fe-Zn zone indicates that ore fluids which deposited the sulfides in the central zone were more saturated with respect to metal sulfides. "

Elsewhere in North Wales, there are occurrences of post-Acadian vein mineralisation that correspond almost exactly to this description. See attached photo. This is a polished block about 25cm in width. I will send you a sample of this stuff too!

18th Dec 2017 10:51 UTCBen Grguric Expert

The fibrous, banded material I examined and had Ernie Nickel perform XRD on from the Lockridge Mine in Devon, definitely contained wurtzite as well as sphalerite. This was published in UK Journal of Mines and Minerals. The visible splintery fibrous structure may be due to prolonged exposure and etching in the mine dump. Possible that fresher material was more compact?

Allan Pring has done some work on banded material from other localities and found it's quite easy to spot wurtzite layers and areas in thin section, as they are not isotropic. If you see previous work of this type in which they claim clearly anisotropic ZnS is sphalerite you really have to ask how can this be?

18th Dec 2017 10:56 UTCJohn Mason Expert

Ben, that sample looks remarkably like the later stuff from Central Wales, for sure. This specimen from Frongoch mine is approx 15 cm in width.

18th Dec 2017 11:46 UTCMichel Blondieau

John, your "schalenblende" is a bit different than the ones occuring in Belgium. These specimens seem far more fibrous.

Already, I thank you for the specimen you'll send. I'll let you know what I'll find, probably in january.

Ben, thank you for these really helpful informations. I will get your paper of 2006 at the end of this week. Do you know references for the Allan Pring papers you mention ?

Again, thanks to all for these advices.

Michel

18th Dec 2017 11:52 UTCJohn Mason Expert

No worries. I've been meaning to get these late sphalerites checked out for years! Glad I spotted this thread :)

18th Dec 2017 23:42 UTCRichard Gunter Expert

Hi Michel:

Wurtzite converts to sphalerite in other settings as well. In the Les Malines District a portion of the sphalerite https://www.mindat.org/photo-553101.html has external morphology that had it previously listed as wurtzite. Further XRD work in the district revealed that no wurtzite exists here.

19th Dec 2017 07:49 UTCMichel Blondieau

Hi W. Richard,

Curious platty (hexagonal ?) crystals were indeed known as "wurtzite" at the french Malines mine. In a nice special issue on that mine published in the french "Le Règne Minéral" magazine, it can be read that there is no wurtzite à The Malines mine and all these crystals are only sphalerite. Furthermore, it seems that there was probalby no wurtzite before; their shape are due to problems during their buildings. The link goes to such crystals but not to "schalenblende" that is also known at the Malines. Analyses of "schalenblendes" from the Mallines mine don't show any wurtzite at all.

Thanks for your help.,

Michel

19th Dec 2017 16:34 UTCChristof Schäfer Manager

Michel,

sent you a copy of the wurtzite chapter

20th Dec 2017 08:09 UTCMichel Blondieau

Thank you Christof for that really interesting paper.

Michel

12th Jan 2018 11:43 UTCMichel Blondieau

Hi all,

Würtzite doesn't appear in any schalenblendes I already have analysed by DRX method ! I suspect there is no more würtzite at all in such specimens but I have again other specimens to analyse.

Michel

12th Jan 2018 21:43 UTCRalph S Bottrill 🌟 Manager

The fine grained schalenblende at Broken Hill contains some disordered wurtzite intermixed with sphalerite (PXRD).

13th Jan 2018 08:28 UTCMichel Blondieau

Hi Ralph,

Nice to know that ! I have seen your specimen :

https://www.mindat.org/photo-583425.html

but you write that würtzite may perhaps be associated with sphalerite.

Here you say that it has been proved by PXRD. Is there any paper on that ?

Maybe, do you have an extra small specimen ? I'd really like to analyse that !

You can send me a PM.

Thank you

Michel

13th Jan 2018 09:53 UTCLudger Krahn (2)

For my diploma thesis (Aachen 1985) and Ph.D. thesis (Aachen 1988) I have analysed schalenblende from the dumps of "Kuckucksschacht" - belonging to the Albertsgrube near Diepenlinchen - and idiomorph sphalerite xx from drill core "Albertsgrube 1" (near Stolberg-Werth). I could not find wurtzite (PXRD, ore microscope)!

I think wurtzite is a very rare and only very subordinate component of the schalenblende in Mississippi-Valley-type lead zinc deposits of the region Aachen/Stolberg/East Belgium.

13th Jan 2018 12:13 UTCMichel Blondieau

Hi Ludger,

Thank you for your help. It's a nice information although on the following page.

https://www.mindat.org/mesg-85-134773.html

it can be read :

"The Diepenlinchen mine produced quite a few good mineral specimens. From the main site beautiful Calcite crystals on colloform Schalenblende are noticeable. The most known specimens are beautifully banded Schalenblende samples. The best ones were found at the Henriette shaft site. The primary sulphide paragenesis is dominated by Schalenblende with a variable content of Galena and Marcasite. The pale layers of the Schalenblende only contain Sphalerite, in the dark layers also Wurtzite may be present."

wurtzite MAY (!!!) be present...

As you, I think wurtzite is really rare and perhaps there is none at all !

For the schalenblendes from Belgium, the presence of wurtzite was first mentionned by Noelting in 1887. It's really old and perhaps (surely ?) false !!!.

Thank you for your helpful reply

Michel

15th Jan 2018 20:06 UTCRalph S Bottrill 🌟 Manager

Hi Michel, I never published this work, it was only 2 analyses, but maybe I should. I only have a couple specimens, it’s was never common, but will look our for some more for you.

16th Jan 2018 06:47 UTCMichel Blondieau

Hi ralph,

Thank you for your help. If you can find a small sample, it would be fine ! Only 1 gram of matter is much more than necessary !

Wurtzite in Schalenblende is curious on the genetic scale too. As wurtzite is the stable ZnS over a temperature of about 1000° (depending of the amount of iron...) and Sphalerite is the stable one below. In Belgium, schalenblende ores were deposited at about 100°C ! It's not really the good conditions for wurtzite !!

Thanks to all for the help.

Michel

16th Jan 2018 10:55 UTCBen Grguric Expert

I've just uploaded an example of the Broken Hill secondary sphalerite and galena at https://www.mindat.org/photo-865684.html

16th Jan 2018 13:03 UTCRalph S Bottrill 🌟 Manager

Thanks Ben, it’s similar to the one I tested.

I’m dubious that all wurtzites formed over 1000C, it’s a bit like saying aragonite is the high pressure polymorph of calcite, but we know it’s forms in seashells and surfical lavas: other chemical and thermodynamic conditions are important too. Ditto for cristobalite and tridymite type silica (high temperature polymorphism) forming in opal near room temperature.

This material probably formed rapidly, at relatively low temperature and some of the zinc sulphide is very poorly crystalline with a mixture of wurtzite and sphalerite polytypes, though sphalerite appeared dominant. We should write it up.

16th Jan 2018 16:16 UTCAlex Homenuke 🌟 Expert

Maybe schalenblende should be redefined primarily as a textural term related to genesis?

17th Jan 2018 20:01 UTCMichel Blondieau

Thank you Ralph for your help.

Michel

17th Jan 2018 20:09 UTCMichel Blondieau

Hi Ralph and Ben,

Schalenblendes from Belgium, Germany or Poland are really different than yours and I'll try to get one sample and analyse it.

I already have analysed more than 10 schalenblendes from different localities and wurtzite doesn't appear ! Sometimes, there are really low reflections that could be suited with but it's not sure at all.

Interesting what you say Ralph about aragonite and other silica polymorphs.

Again, thanks to all,

Michel

21st Jan 2018 17:00 UTCPhilip Bluemner Expert

Hello,

I first learned that schalenblende consists of sphalerite and can contain wurtzite (and other sulphides). But over the years I heard that schalenblende also can be solely wurtzite, like here from Silbereckle.

The person I bought it from said all specimens are wurtzite. According to above knowledge I never had it analyzed.

Best regards

Philip

21st Jan 2018 17:26 UTCMichel Blondieau

Hi Philip,

Thanks for your reply

I already have seen your nice schalenblendes here on the forum.

As everybody, I heard and read that wurtzite is common in schalenblendes. With XRD method, I want to prove it and it isn't easy at all. If you agree, I can do an analyse on your schalenblende from Reichenbach. It would be interesting to do an analysis as that locality is effectly described to contain wurtzit.

I only need about 1 gram of matter. In fact, I can do with less than that quantity but I have to select carefully what I have to analyse (no galena or others...)

If you accept, you can send me a PM.

Thank you Philip for your help.

Michel

21st Jan 2018 20:27 UTCMichel Blondieau

Hi Phillip,

In the joined picture, it can be read something about the schalenblende from the area of Reichenbach.

Noeling, 1887, in german.

Michel

3rd Feb 2018 12:25 UTCMichel Blondieau

Hi John

Thank you for the samples you have sent.

I do an XRD analysis on the nice fibrous material from the Clara Mine at Ponterwyd but halas, I only have seen sphalerite and no wurtzite at all !

I have sent you an PM

Wurtzite in schalenblende is really hard to prove !!!

Michel

4th Feb 2018 13:38 UTCMichel Blondieau

"Wurtzite" from Pribram is only sphalerite too !!!

Wurtzite seems to be a very rare mineral !

Michel

4th Feb 2018 14:33 UTCPaul De Bondt Manager

Michel,

There is schalenblende from Pribram too but unfortunately I was never able to obtain a specimen.

So I can't help you but perhaps another member has a specimen for you.... and one for me.

A bientôt a Hannut.

Paul.

4th Feb 2018 16:36 UTCMichel Blondieau

Merci Paul,

A bientôt à Hannut,

Michel

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