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Identity HelpPossible CT Rt. 9 Chalcocite

14th May 2016 17:33 UTCJacob Zonderman

Recently purchased a Connecticut azurite specimen labeled as coming from New Britain. After more inspection it looks like there is some massive bornite (or broken Chalcocite) and many mm sized xtls and one sharp 1x1 cm xtl that I believe to be Chalcocite. Also present malachite, possible chrysocolla and quartz. Looking for confirmation and rarity (as far as I can tell it is rare already, and size is rarer) and possible value estimates if possible. Thanks.

14th May 2016 18:41 UTCHarold Moritz 🌟 Expert

Bornite is typically much more common in these veins than chalcocite, and the rather rounded crystal habit is typical, as is the purplish tinge in the first photo. Hard to say in the bottom one, but I am leaning toward bornite. I have usually only seen malachite form from chalcocite, so perhaps the presence of azurite, too, suggests bornite? But azurite is very much rarer in Conn. so that association may be only coincidence...

15th May 2016 00:20 UTCJacob Zonderman

I figured that the first photo is bornite after comparing it to the one you have posted from the locale, but the larger xtl looks like a larger version of one of the chalcocites posted (the 2 posted are micros). There are some small tabby-ish formed xtls like this but this one is the largest by far and clearly shaped, and its that shape that had me leaning towards chalcocite (I agree the bornite I have seen is more rounded in nature). The back is flat. I didn't photograph the bottom but that is where most of the azurite is. It looks like it formed either on top of now dissolved quartz or it is an epimorph after quartz. There is also some residual quartz. I could photograph that as will if you would like to see.

15th May 2016 01:46 UTCsteven garza

Dear Harold & Jacob;

It might help to read Hydrothermal barite deposits of Rt. 72, New Britain; if you read the last paragraph, so you know where I come from. MOST of the articles, other than the most common ones, were my finds, all of which were confirmed. The specimen Jacob has, probably originally came from Nancy Speed (was Koski, at that time), who, with Chris wong, recover quite a bit of this mineral, which came from a good sized hit, on the (then) Rt. 72 bypass, which USED to end at Fieneman (misspelled?) Road. on the Farmington border to that new road. The alteration zone was pretty isolated, very shallow, & a foot or less above the basalt/red siltstone boundary. The only other place the had a blue copper mineral, was just W of where the bypass branched off from Rt. 72, proper. That was the hit of diabolite, I made; I think one other person got some specimens, as, when I went back, the place was dug out.

I believe your specimen is correctly ID'ed, &, the xl is a bornite. Added, the bornite & chalcocite usually were together, the bornite as xls & the chalcocite as massive. I have pieces, where the 3 (chalcopyrite, chalcocite, & bornite) are intermixed, with ribbons of color going all over, making it look like a mineral "salad"! I suspect the reason the diabolite formed, instead of azurite, at the one area, is because there was so much galena there. Several members of the Boston club collected there, with me, &, I was the person who led the Boston Mineral Club's trip (mentioned in a Rocks & Minerals or MinRec article (getting too old for this)).

Your friend, Steve

Quick PS The azurite was as you see there; the diabolite are sharper, clearer, & a different shade of blue.

15th May 2016 02:07 UTCHarold Moritz 🌟 Expert

Steve:

Thanks for the details, must have been a fun time collecting there back then! I have that publication, thanks. All 3 copper sulfide minerals do occur together there, just that it is difficult to tell in a photo the difference between chalcocite and bornite. Would love to see an analysis confirming the diaboleite. The presence of a Cl-rich mineral in these veins would be very, very unusual, especially as it has not been reported anywhere in the eastern US. Worldwide, many of the localities are slag piles.

15th May 2016 02:09 UTCJacob Zonderman

Is there anyone who could identify without damaging the specimen? I've been considering it for some time with other specimens I have, just don't want to damage them to get a result. And with this one I am very curious with all this new info.

15th May 2016 03:28 UTCsteven garza

Dear Jacob;

Good point, until you remember that underlying all this was a marine sediment environment, which why the marble bodies, from RI to NY border area. Since the hydrothermals passed through those beds, occasional Cl, wouldn't be out of the question. The Pb that formed the galena, probably was a small impurity, in other minerals, at the same time, & so was the Cl. As the material I had tested came from the other side of the same knob the galena was, &, both sides had some some alteration, the Diabolite side a little worse than the galena side, but, all part of the same vein network, I think the Cl probably came from those decomposed ferroan dolomites & siderites, on that side. Cl is VERY common impurity, in vein type carbonates. Added, these veins also had a LOT of anthraxolite ( not mentioned in the article, because it's not a mineral; that vein was LOADED with it, though); all life need Cl, so, that is the likely source, also.

Your friend, Steve

15th May 2016 14:35 UTCHarold Moritz 🌟 Expert

Jacob:

The best non-destructive testing is Raman spectroscopy. Sadly, the equipment doesnt grow on trees. Ask around at the New Haven club meetings to see if someone knows where you could get it done.

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