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Today's quiz: Arsenopyrite, lӧllingite or ? From ?

Posted by Modris Baum  
Re: Today's quiz: Arsenopyrite, lӧllingite or ? From ?
February 03, 2012 10:48PM
    
Hi Peter,

Yes it was Wilfried. But I don't think it was from him. All of his stuff was carefully labeled and I have tried to keep it carefully separate from everything else. Of course I do screw up - regularly! Anyway it was around 1995.

Regarding the matrix, after a more careful look, it seems that the arsenopyrite/lӧllingite as well as the mica is confined to bands that are mostly feldspar (?), whereas the adjacent analcime is pretty barren except for the one lone black prismatic xl.

Given that, it's not out of the question that it's from MSH. But the arsenopyrite/lӧllingite would be way better than anything I have seen from there . I can't understand why I would have dumped it in a "miscellaneous" box if I knew it was from MSH? But I have zero recollection of even seeing this specimen before. Maybe I just never looked at it with a scope!

Modris
Re: Today's quiz: Arsenopyrite, lӧllingite or ? From ?
February 03, 2012 11:53PM
About three years ago I collected a silvery mineral from Franklin that I thought was Lollingite, Galena, or Arsenopyrite. It was really dense and heavy. Some specimens were hand sized plates. They came from an augen in the Franklin Marble forming the walls of the Passaic Pit, Sterling Hill Mine.

It would have been a huge bonanza if it was Lollingite. I finally had a piece analyzed and it was Galena. Still a nice find.

The attached picture is from two small pieces I could locate without having to ransack the basement. Note the foliated habit expressed by the shiny surfaces. There is no real cubic aspect to the galena in these specimens. They have a more tabular structure. Unfortunately Lollingite and Arsenopyrite also can have a tabular or compressed structure. Look up the minerals, and look at the various crystal structures shown.

The matrix may be calcite. More particularly, Franklin Marble. Check and see if it fluoresces red brightly under short wave fluorescent light or perhaps faintly under a regular black light. If it does it is probably from Franklin. But then, if they don't fluoresce they may still be from that area, just not from the vicinity of the zinc ore.

You might want to look at Dunn's description of arsenopyrite from the Franklin Mining District on this web page.

[franklin-sterlinghill.com]

In the description, he mentions chevron structure which these crystals seem to exhibit.

Good Luck,
Mark
Attachments:
open | download - galena.jpg (67.4 KB)
Re: Today's quiz: Arsenopyrite, lӧllingite or ? From ?
February 04, 2012 12:49AM
    
Hi Mark,

Interestingly enough, I have some samples of galena from the Passaic Pit that are very similar to yours.

In fact, I was going to post some photos because there aren't any galena photos from the Pit on Mindat and because some of the samples have a very beautiful iridescence. Also, some of this stuff is the host for the cerussite at SH. (I'll probably post in a couple of days - once I'm done with a few more micros.)

Regarding the material we have been discussing: It's pretty clear to me now that there is a lot of analcime in the matrix which pretty much rules out Sterling Hill. There is a weak cherry red fluorescent response. But albite at MSH (etc.) has a similar response and there seems to be some feldspar in the matrix as well.

I did test for calcite with HCl and got some bubbles - but it didn't last very long. Can't be very much there.

As for it being arsenopyrite - that seems likely now. But I want to do the test for lӧllingite first before declaring victory.

Thanks for your interest - Modris



Edited 1 time(s). Last edit at 02/04/2012 04:18PM by Modris Baum.
Re: Today's quiz: Arsenopyrite, lӧllingite or ? From ?
February 04, 2012 02:54PM
Hi Modris,
sorry for the delay, but I just now found time to get down tot he basement and to check my specimens. Some Tuften (aka AS Granit) specimens look a lot like yours, but they are from recent years, maximum 3 years ago. So too late for our swap.
It may (or may not) be an arsenopyrite from Björndalen Quarry in Tvedalen - a swap in 1995 might fit with the specimen being a few years older. There's a comparable one in my collection (which is not the counterpart of yours, though). Unfortunately I do not remember after all these years, what I sent you. So this probably doesn't help either.
Take care
Wilfried Steffens
Re: Today's quiz: Arsenopyrite, lӧllingite or ? From ?
February 04, 2012 04:27PM
    
Hi Wilfied

Good to hear from you. Thanks for the response.

As I mentioned, I have kept your stuff separate. So it would have to have been one of those "senior moments". You know: "Let's see what this is. Oh wait, the phone is ringing. ... Now where was I? Hmm - couldn't be important." But then what happened to your label?

Anyway - I'm now thinking that it's from MSH after all. But I don't think I'll ever be able to prove it.

Horváth does mention arsenopyrite to 1.5 cm from marble xenolith at MSH. But this isn't from that environment and I can't really place it in any of the "typical" MSH environments that I'm familiar with.

Best regards - Modris



Edited 1 time(s). Last edit at 02/04/2012 04:28PM by Modris Baum.
Re: Today's quiz: Arsenopyrite, lӧllingite or ? From ?
February 21, 2012 01:58AM
    
Well - I did my "homework". But to no avail.

The acid I had in the ground glass stoppered bottle is just HCl (probably concentrated).
After about 11 hours, the grain of arsenopyrite/lӧllingite has done absolutely nothing in the stuff.
But the acid is happy enough to munch on calcite - even after 20-30 years.

So now I have to decide if I really want to get 500 ml of nitric acid. (Or if I even can. Maybe you have to be a school or some such?)

Modris
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