FMF - Friends of Minerals Forum, discussion and message board

[Pete Richards]

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.

[Pete Richards]

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!

[Bob Carnein]

It may be bloedite (whitish) with krohnkite (blue).

[Bob Carnein]

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.

[Don Lum]

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

Don

[Peter Lemkin]

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 spheroids can be highly polished by friction or rough.
Commonly, they are labeled 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
(link normalized by FMF)

[marco campos-venuti]

There are many minerals making nodules with the same fabric. Barite also is a good guess, you can check density.

[Peter Lemkin]

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 go 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?

[Pete Richards]

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.

[Pete Richards]

Next in this intermittent series - a fairly nice kyanite specimen without a locality. No staurolite is present, just kyanite, silvery mica, and the only thing that might reveal the locality - black tourmaline. No guess whether it is schorl, dravite, uvite, or yet another dark tourmaline.

Does the association of kyanite and tourmaline suggest a locality to anybody?