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

Click on title at top of page to see the photo.

This is a bit embarrassing:

I have no recollection of when, how or why I got this. I'm not even sure if it's arsenopyrite, lӧlingite or something more exotic.

And I have no clue regarding location - other than that it does not look like anything from the places I have collected at: Franklin (area), MSH, PA or Maine.

Given the recent spectacular success of my last few queries, I'm expecting a resolution as soon as I click send

Thanks - Modris



Edited 1 time(s). Last edit at 02/02/2012 08:37PM by Modris Baum.

Reminds me a bit of dyscrasite.

Hi Alfredo,

I see what you mean - and dyscrasite would be cool.

But where the heck could I have gotten it? I strongly suspect (but don't recall) that some local collector gave it to me. Of course he could have found it anywhere. But I don't see any dyscrasite localities listed for US or Canada.

Note: The "color" is very silvery - just like lollingite and arsenopyrite.

I suppose I could have bought it and forgotten - but it's not the kind of thing I'd normally buy.

Modris

Photo's not that great, but reminds me of Tremolite.

Goodluck,
Craig.

Hi Craig,

I think the problem is that the reflections make it look white, whereas my intention was to capture the silvery metallic luster.
Also, the xl is still patially embedded so the shape may not be clear.

I replaced the photo with one of a smaller xl. (This was already there as a stereo child photo, but maybe this mono shot is more useful in this case.)
I put the original parent as another child photo.

Modris

Hi Modris,

Yes you are correct, I was seeing it as white.

After looking at the other photo's, I think you maybe correct about it being Arsenopyrite, as far as look goes anyway.

My guess now, just to give you another avenue would be Pearceite.

Goodluck my friend,
Craig.

Yes, under this new light angle it does look more like an arsenopyrite.

OK - thanks guys.

But I have a feeling I'll never know from where. No big deal.

Modris

Don`t give up that quick, its a nice specimen
I worked a bit on the pic, hope it fits and help others by the ID.

Well, it did remind me of arsenopyrites I've collected at Sagåsen quarry, occuring in analcime matrix with minor calcite, mine wasn't that nice though... Have you traded with Tomas Husdal?

Peter

Just a stab, but I have seen similar Mexican specimens also.

If you place a small piece ( approx. 0.1mm) in concentrated nitric acid, if it is arsenopyrite after about 12 hours or less you will have a pseudomorph of fine grained yellowish sulphur left behind. If it is loellingite you will find a lump or pile made up of relatively coarse grained white-grey crystals of arsenic oxide.

Thanks folks!

Peter - interesting suggestion. I haven't traded with Tomas but I did trade a bit - years ago - with a German collector with a great interest in Norway.

Also interesting regarding the analcime. When I was looking at the white stuff in the matrix I was saying to myself "Gee, this looks familiar." I decided it must be quartz, but now that you mention it, it really looks more like analcime. It would be ironic if I actually did find this myself - at MSH. But for MSH this would really be killer arsenopyrite!

Reiner - thanks for the tip. I don't have any nitric acid but I'll see if I can get some. Sounds like a very useful test.

Modris

Chris,

Looks like you sharpened the photo and/or increased contrast? Did you use a "global" tool (like "auto levels") or seperate steps?
On my monitor your version looks too blue/purple. But mine now looks too green. The truth may lie somewhere in the middle.

Modris

No I used separate steps with Nikon Capture and yes its still a bit too purple also here.

Peter,

I tried measuring the average specific gravity of the samples using a modified Archimede's method.

I used a kitchen scale that measures only in ounces and is probably accurate to 0.1 oz at best so my results are probably not definitive.

The samples weigh 1.3 oz; an equivalent amount of water about 0.6-0.7 oz - say 0.65 oz.

So the specific gravity could range from a high of 1.4/0.55 = 2.55 to a low of 1.6.

The low number is not plausible, but even the high number seems to exclude quartz (especially given the mica inclusions - ~2.8)

But the the range does cover analcime (2.27) "comfortably".

Reiner,

Turns out I may have some nitric acid left over from more ambitious days (i.e. before I burned holes in my shirts).
It's been sitting for many years, safe and sound, in a ground glass stoppered bottle.

But I can't get it open. Heating with hot water hasn't helped so far. Any suggestions?

Also - is there an easy way to tell if it's nitric or hydrochloric? I neglected to label it. The color is quite yellow - but maybe I already used it on something.

Modris

Those glass stoppers can really seize on. Last time that happened I had to use pliers and turned it while pulling up to loosen it, hopefully it will turn before breaking. Wearing rubber gloves while you do it would be a good idea. Maybe soak it in water overnight as well first to dissolve some of the deposits that have probably seized it on. The smell will tell you what it is, but don't stick your nose up to it, waft some towards you with your hand. A sharp acid smell is HCL a more fresh smell ( hard to describe) is nitric acid.

Modris
If you have kept the acid after it has been used and you think it contains contaminants I would not use it. I would suggest that you dispose of it appropriately and purchase somw fresh acid for you tests
Cheers

For anyone who still cares, I posted a new version of the original photo.

This time I picked away a bit more of the matrix and concentrated on trying to show the shape of the xl rather than trying to show the silvery luster.
There are still some areas that are close to "blowouts" (i.e. white looking) but mostly not.

With this exposure, the background also looks more natural (lighter) because it wasn't as badly underexposed as before.
(However, the stuff here looks more like feldspar than the "analcime" on the rest of the specimen.)

Modris

Reiner

Thanks much. If I can't get the stopper unstuck I guess I'll have to get some from Ward's - 500ml minimum (yuck)



Edited 1 time(s). Last edit at 02/03/2012 10:20PM by Modris Baum.

Matrix really looks alkaline... Both arsenopyrite and löllingite occure in our alkaline pegmatites, and there is no way to distinguish them visualy is my excperience. It's getting darn difficult to get chemicals in Norway these days, but I'll try to get some nitric-acid, would be fun to test out...

Was it Wilfried you swaped with (if it is, it's not the Sagåsen material I thought of... it was found by Husdal in 2009 or 10, and it was also rich in bertrandite...)?