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Minerals and mysteries from a college collection
  
  Index -> What is it? - Where is it from?
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Pete Richards
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PostPosted: Oct 19, 2021 19:49    Post subject: Minerals and mysteries from a college collection  

I'm back to working on the local college's mineral collection - which needs a lot of help. This interesting specimen is labeled bloedite, and claims to be from Chuquicamata, Chile. Part of it certainly looks like chalcanthite. I'm hoping there are some folks who know the mineralogy of this area and can help with identification.


IMG_4096.jpg
 Locality:
Chuquicamata District, Calama, El Loa Province, Antofagasta Region, Chile
 Dimensions: 3x5 cm by 2.5 cm thick
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IMG_4096.jpg



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PostPosted: Oct 19, 2021 19:53    Post subject: Re: Minerals and mysteries from a college collection  

Here's one that looks kind of like a petrified golf ball - and is about that size. I'm not even sure whether it is a mineral, a rock, or a fossil, though I lean toward the latter. Does anybody recognize this and know of a place where such things are found? A wild guess would be some kind of a cycad seed pod. Enlighten me!


IMG_4097.jpg
 Dimensions: 3 cm diameter
 Description:
quite possibly silicified
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IMG_4097.jpg



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PostPosted: Oct 19, 2021 20:05    Post subject: Re: Minerals and mysteries from a college collection  

It may be bloedite (whitish) with krohnkite (blue).
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PostPosted: Oct 19, 2021 20:08    Post subject: Re: Minerals and mysteries from a college collection  

I'm seeing some iridescence in the freshly broken half. Do you have any information on the streak, hardness, SG? It looks somewhat like the marcasite concretions that sometimes contain pyritized fossils from New York state.
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PostPosted: Oct 19, 2021 21:10    Post subject: Re: Minerals and mysteries from a college collection  

Dr. Richards, I have posted a picture of a Kröhnkite, Blödite specimen from the
Chuquicamata Mine, Chuquicamata District, Calama, El Loa Province, Antofagasta Region, Chile from my collection. I know looks can be deceiving but my specimen is very similar to the one you posted.

https://www.mineral-forum.com/message-board/viewtopic.php?p=42352#42352

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Peter Lemkin




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PostPosted: Oct 20, 2021 01:24    Post subject: Re: Minerals and mysteries from a college collection  

I'm 99.9% sure I know the radiating ball mineral. I have many in my collection. It is Apatite (Var: Carbonate-rich Apatite) Ca5(PO4)3(Cl/F/OH) from the Khmelnytskyi Oblast, Ukraine. There is an image of one at mindat: https://www.mindat.org/gallery.php?frm_id=pager&cform_is_valid=1&min=29229&loc=&u=&potd=&pco=&d=&showtype=1&phototype=0&checkall=0&filtmin=0&filtassoc=0&filtcountry=Ukraine&loctxt=&keywords=&orderxby=0&submit_pager=Filter+Search
The ones I have in my collection are usually very regularly spherical and show the radial growth patterns characteristic of this variety when broken apart. Color ranges from muddy green-brown to brown - even almost black, with a little bit of luster on the small fibrous apatite. The outsides of the shperoids can be highly polished by friction or rough.
Commonly, they are labled as phosphorite and there is a better photo of one split open here: https://www.mindat.org/loc-3277.html
There is another article on them - which to my knowledge only form in such large balls in this one location here:
https://commons.wikimedia.org/wiki/File:Black_phosphorite_nodule_Nagoryany_Formation,_near-uppermost_Neoproterozoic;_Ushytsya_River_area,_Khmelnitska_Province,_Ukraine_1_15137118687.jpg
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marco campos-venuti




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PostPosted: Oct 20, 2021 06:20    Post subject: Re: Minerals and mysteries from a college collection  

There are many minerals making nodules with the same fabric. Barite also is a good guess, you can check density.
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PostPosted: Oct 21, 2021 01:29    Post subject: Re: Minerals and mysteries from a college collection  

Yes, of course, check density and hardness - but I'm still almost sure it is a 'phosphorite' [hydroxyapatite] from Ukraine. When I lived in the USA or W. Europe I don't remember ever seeing them for sale. Here in Czech Republic when I do to shows they are fairly common....but then one can drive to Ukraine during a long day's drive, and there are many Ukranians here, including mineral dealers and collectors. The difference in density just hand-held between apatite and barite would be immediately noticeable. Yes, there are even other fibrous spherical minerals, but this one has a very characteristic way it looks when broken open. This one at the museum, nor those I gave links to do not, but some have a very small void in the center. They formed in a geological formation near a river and many are found water-rounded in the river. These are very nice in a collection, with their very smooth exterior, like a petrified egg.

By the way, the location for these phosporites is not among the choices on this forum, even though it is listed at this location on Mindat. How does one get a new location made 'official' here?
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PostPosted: Oct 21, 2021 09:09    Post subject: Re: Minerals and mysteries from a college collection  

Thanks to all who offered suggestions about my first two mysteries!

Thanks, Don, for suggesting kröhnkite; I had also thought of that, and it fits.

Peter, your phosphorite nodule is extremely similar to what I have, though I have no idea how a nodule from the Ukraine wound up in Ohio! The form and the detailed structure seem to be very much the same. It is clearly not dense enough to be barite, though other concretion-forming minerals would be possible.

While confirmatory tests will be sought in both cases, having a strong indication of what to look for is very helpful.

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