FMF - Friends of Minerals Forum, discussion and message board

[Tracy]

I recently acquired an unusual specimen described as botryoidal stibnite from Felsobanya, Romania. The mineral was confirmed as stibnite by Marcus Origlieri of Mineral Zone, using X-ray powder diffraction. Marcus also mentioned that it has a radiating structure which is consistent with stibnite.

Several things about this specimen are puzzling. First, I have never heard of botryoidal stibnite, though I am told it is theorectically possible. Second, a strange old typed label accompanying the specimen describes it as "radial crystals on ore" but it was subsequently written on by hand with the words "stibnite" and "Felsobanya, Rumania." [Based on the fact that the label at the bottom gives the specimen number which was typed on the label and the price which was handwritten on the label, plus the fact that the paper label and the specimen label were made using a similar typewriter, I'm guessing that these two events most likely occurred at or around the same time and by the same person or people.] I believe that it is stibnite as confirmed by Marcus, but trying to find out anything else beyond that it is challenging.

Has anyone else ever seen or heard of botryoidal stibnite, either from Romania or from somewhere else? Some photos are attached of the specimen (about 6.5 x 4.5 x 3.5 cm) as well as the label. The piece has a generally smooth surface with a dull, dark color varying from gray to olive-gray. Some areas are coated with microcrystals.

Tracy

[Jordi Fabre]

No doubts about Stibnite not only due the Marcus analysis but also by its shape and radiating structure. The top is not so evident but I guess that it could be Stibnite. Also it could be Berthierite, the iron antimony sulfide, which on Romanian deposits grows frequently together with the Stibnite, the antimony sulfide.

Speaking about Romania, Felsöbánya is the former name for the modern Baia Sprie. Both mean the same: upper mine. Felsöbánya is the Hungarian name and Baia Sprie is the Romanian name.

Jordi

[Gail]

Jordi, you are a walking encylopedia!

[Tracy]

Thanks Jordi for your comments and observations!

The top of the specimen was extremely hard to photograph. I tried several times and couldn't capture the color properly. What I can tell you is that the olive-grey color of the tarnished areas is very similar to what is shown in the berthierite specimen featured on the mindat page for berthierite (berthierite/boulangerite from Muramures, photo submitted by "ciuturas"). Also, looking under 10X magnification, in the crystalline areas I can see two types of "microsprays" - one type has very bright, shiny silver crystals and the other has darker gray-black crystals (sorry I can't provide a close-up photo). Last, looking under magnification I also see that the surface of the specimen, when viewed from a certain direction, has a fibrous appearance to it which, judging by the photos I looked at, could be consistent with a berthierite crust.

Could this specimen therefore be stibnite coated with berthierite, and not "true" botryoidal stibnite? (someone else might have to study it in person to give me that answer) Either way, I'm relieved to know that it is Romanian stibnite, just as the label says. Thanks!

- Tracy

[lluis]

Good morning, Tak/List

Well, test for iron is easy and then you could know if stibnite or some berthierite is there.

Do you know anyone with some lab? Not special reagents, some hydrochloric acid and ammonium thiocianate...?

With best wishes

Lluís

[Tracy]

Hi Lluis -

I'm afraid that I don't have easy access to lab chemicals (unless I ordered them and set up a proper work/storage area for corrosives in the basement). How easy are the tests you mention? I did notice a couple of brown patches along one edge of the specimen which suggested to me that there might be some iron - I assumed it was incidental and haven't studied that area too closely since. I can post a photo tonight if it would help.

Thanks,
Tracy

[lluis]

Hi, Tracy/List

It is easy: some dust, a drop of hydrochloric acid reagent grade (without iron), some time (five minutes) and a drop of a solution of the ammonium thiocianate.
If a blood red developes, then Iron


If you could send me a sample (some scratch) I could do it for you. I am chemist and I love chemistry :-)
So, any opportunity is *great* :-)

Brown is not necesarily iron. The stibnite could also alter to antimonium oxides, that are brown

With best wishes

LLuís

[Tracy]

I went back to check with Marcus who assured me that the specimen is 100% stibnite, as confirmed by X-ray, and that there is no berthierite. He thinks it is a nice reference specimen of botryoidal stibnite. I didn't ask about the locality because the label predates him, but the responses suggest that Felsobanya is at least reasonable.

It's not pretty, but it is unusual - unless anybody knows of other botryoidal sibnites, from Romania or elsewhere...a fun acquisition for me regardless.

Thanks Lluis for your offer, but I'll leave the specimen alone for now. And thanks all for the input.

Tracy