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Identity HelpBelieve this is botryoidal chalcedony...

28th Oct 2019 17:36 GMTJames Perot

But I cannot find a anything this large online.  I got this and 4 more at an auction of a 97 y.o. collector (this one is the smallest of them all) so not sure if  maybe it came from an old site or I am the worst internet searcher of all time.  
I find lots of smaller "pieces" that look like it but nothing so big...???
It measures ~12" by 12" and weighs a bit over 10.5 lbs.
Any information would be greatly appreciated!
Thank you in advance.

28th Oct 2019 17:39 GMTJames Perot

Here is a side view...

28th Oct 2019 17:57 GMTGeorg Graf

Hi James,

from the  Krunkelbach Uranium Deposi, Black Forest, Germany

I have similar specimens. Quite small, but I see no reason, why this material should not occur in bigger pieces. On the Menzenschwand specimens one can see also dendritic appearing material, concretely: Hematite.

Kind regards, Georg

28th Oct 2019 17:58 GMTGeorg Graf

Ah yes, it´´  s Calcedony.

28th Oct 2019 18:33 GMTPaul Brandes Manager

Looks like chalcedony with a coating of drusy quartz. However, this type of material could be from anywhere.

28th Oct 2019 19:43 GMTKevin Conroy Manager

Paul's right, druse quartz on chalcedony.   The brown is limonite/goethite after marcasite or pyrite, and the cream colored masses toward the center and right are weathered baryte.   This is almost certainly from one of the old baryte mines (not Pea Ridge Mine) in Washington County, Missouri, USA.   Please see:   https://www.mindat.org/gallery.php?loc=24600&min=3337

28th Oct 2019 20:18 GMTBob Harman

I agree.   This combination is quite common in the Midwest.    Some examples make nice full cabinet display specimens. For reference, two Indiana examples from my collection.   CHEERS.....BOB 

28th Oct 2019 20:20 GMTBob Harman

And my second example.     BOB

28th Oct 2019 21:01 GMTKevin Conroy Manager

If you would like to read a little on the Potosi Formation (Potosi Dolomite) see page 182 of:

29th Oct 2019 21:03 GMTMichel Gadoury

Hello to you, I would like to be able to obtain a more precise localization for these specimens. All I know is that they come from Wayne County, Missouri, USA. They are composed of drusy Quartz and some of them seems to be cast from now a gone mineral (baryte?).All comments are welcome.

30th Oct 2019 01:08 GMTKevin Conroy Manager

Unfortunately the drusy quartz from the Potosi Formation doesn't have a characterstic look by location, so there's no way of telling an exact location for these.

Also, I have never heard of any outcrops of the Potosi Formation as far south as Wayne County.   Did you collect these, or did you obtain them from someone else?

30th Oct 2019 16:33 GMTHarold (Hal) Prior Expert

This is highly likely to be Washington County, or nearby. About 55 years ago Glenn Williams and I collected many flats of the druzy Q. from numerous areas of Washington County. We wholesaled many flats of it – the decorators loved the big (8” or larger pieces). We called it “Cow Pasture Quartz”, as many of the best spots were converted into Cow pastures with literally 100’s of specimens on the surface. Glenn being a non-farmer, would get very nervous when 20-30 very large cows would surround us as we wandered through their domain. I think they were more curious than aggressive. A couple times a large Bull would convince us to rapidly depart! A that time you could also collect easily nice “Crested Barite”, with combos with the DQ. I loved Washington County 55 years ago. You could find barite almost anywhere the soil had been disturbed. It was so plentiful that I only saved a few specimens.

30th Oct 2019 17:53 GMTKevin Conroy Manager

Hal, a few of my favorite collecting spots have homes on them now!   The wild thing is that the old barite mines weren't reclaimed, they just put homes among the overgrown pits!!

30th Oct 2019 20:36 GMTMichel Gadoury

Hello to you both, and thank you for your answers as well as to have shared your memories. 
I obtained this flat from a dealer a few years ago. I have always doubted the locality. Now I'm pretty shure it's probably more likely to be from Washington County.
Thanks again for your help.

1st Nov 2019 22:57 GMTJames Perot

Have had some technical difficulties but, at first chance, wanted to thank you all for the help.  From your tips/photos/combined expertise, I have to say that I am completely in agreement with your assessment.  A search of Washington County turned up tons of examples like mine....mystery solved!  Thanks to all!
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