FMF - Friends of Minerals Forum, discussion and message board

[bugrock]

Hello,

I recently acquired a very dense specimen labeled as native bismuth with the following location:

Schacht 371, Schlema-Hartenstein, Saxony, Germany

It is a heavy piece for the size of the specimen and looks like a "floater". Externally the specimen
has nice crystals of "silver-lead colored" bismuth and there is also a purplish sheen on some of the
surfaces that do not host crystals. After receipt a few questions came to mind:

1) Given the weight of it, could the entire specimen be massive bismuth with xls on the surface?

2) #1 could be checked by measuring a specific gravity providing there are no matrix rocks
known from the location that have a specific gravity close to that of bismuth metal. Can I proceed
to check the specific gravity and arrive at an answer to #1?

3) I've seen those brightly colored manufactured purple/blue colored bismuth crystals that
are on sale in rock shops and at shows. Hmm.....could the piece I have be an earlier version of these
modern "designer" pieces? In other words is the specimen I have not directly from the mine but from a
smelter or processing plant?

Would greatly appreciate learning more regarding this German location, the habits exhibited by native
bismuth there, and the methods used to process the metal. Is this location known for "mine artifacts" of
bismuth metal?

Very much appreciate comments and suggestions,

George

[alfredo]

That is the way native bismuth from Germany can look. I see no reason to suspect that it is was manufactured.

[mmauthner]

I have had several such pieces in my collection. Looks perfectly reasonable to me.

mark

[bugrock]

Hello,

I very much appreciate comments on this piece.

Sounds like it came directly from the mine.

But is it solid bismuth through and through? Based on the perceived density of the
piece it weighs in the hand like solid metal. Has any one cut through such a piece to prove that?

Thanks again,

George

[Peter Megaw]

There is a formula in Sinkankis's "Gemstone and Mineral Databook" that lets you calculate the contribution of two different species to the collective specific gravity of a specimen. (I'm traveling so I can't provide it now). Most easily used for determining contribution of gold to a gold in quartz specimen (some gold dealers pretend this is www.spam.org science...but it's pretty simple...Alfredo can probably recite the formula in his sleep), but potentially useful here, especially since you know the specific gravity of one species, so you can work out the proportion of the total bismuth represents and then come up with a likely candidate for the other...as well as its proportion. Things get more complicated with more than 2 species, but your photo looks like two dominate here.

G&MD is long out of print but an incredibly valuable resource for practical mineral-related data (including cleaning) I strongly recommend getting a copy if you don;t have one. John was years ahead of his time in organizing data and the section on recognizing fakes is alone worth the price. Fakers may have gotten more sophisticated, but the basic things that tell you something's wrong have not changed that much. Given some of the things coming out of Asia and northern Africa these days, being up to speed on this pays off.

[keldjarn]

George,

congratulations with winning the Bismuth specimen on the e-rocks auction. I think you can assume the entire specimen is native Bismuth with crystals on top. It looks exactly like a number of such specimens that have been on the market during the last 2 decades. But it is a nicely xlized one and at a fair prize - so enjoy your specimen !

Knut

[arturo shaw]

And the seller, Schani from Burgos, Spain, is somebody that I respect. I've never have any problem with any mineral comming from him. Case it could be of any help... :-)

Nice specimen, don't know why I didn't participate in that auction... :-)
(Any way I loose many more minerals than I get :-( )

Arturo

[Jordi Fabre]

Sure George, it is natural, no doubts about it.

Of course the Calcite matrix the matrix has been dissolved by acid to expose the crystals, but the vast majority of Bismuths from this locality passed the same process.

[arturo shaw]

wow!! A big one with nice crystals.

I will have to save some money for something like this!

Best wishes

Arturo

[bugrock]

Again, I appreciate the comments on the specimen.

Also thanks Peter for the book recommendation.
Will look into this.

Did not know these specimens were acid treated to remove calcite.
Was the calcite only massive or did it sometimes occur
as crystals along with the bismuth? Did the location produce
any combination pieces or calcite crystals with inclusions
of bismuth?


George

[Thomas Uhlig]

Most of the crystalized Bismuth specimens from the Schlema-Hartenstein district are overgrown by massive Calcite and/or Dolomite. This on the one hand requires an acid treatment, but on the other hand it conserves the crystals. Most of the etched out pieces were found on the dumps of Shaft 371 and 38. The first picture below shows such an etched piece from Shaft 38 Schlema.

Massive Bismuth specimens up to 10, 20 or more kg have been found quite often on these dumps. A few years ago a dealer in Freiberg sold them per weight for € 5 per kg. These specimens have no real crystals, but some indistinct crystal faces or etch figures.

The real rarities from the Schlema-Hartenstein district are unetched specimens with free grown Bismuth crystals up to 4 cm on Dolomite or Siderite crystals. These are probably the world's best Bismuth specimens and very, very sought after. Second picture below shows such a famous piece from the "Opal" vein of Shaft 38 Schlema with crystals up to 2.5 cm on Dolomite. The third picture shows very sharp und lustrous Bismuth crystals up to 0.6 cm on Siderite from Shaft 371.

[bugrock]

Thomas,

I greatly appreciate the information and the images of the
attractive bismuth specimens. Great combination pieces
and have never seen specimens of this type before.

In the case of the massive bismuth pieces, are they of
interest to collectors or used as a source of bismuth metal?




George

[bugrock]

Thomas,

It occurs to me your could add your images to
mindat. Took brief look and I don't see specimens
like those you posted on mindat.

George

[jimB]

The first specimen I was ever truly captivated by was a bismuth from Schneeburg, Saxony (Wilbers). Thus I enjoy seeing the species / locality in pictures here. These are wonderful things. Thank you to all who posted.

[Thomas Uhlig]

Hi Jim,
the Schneeberg and Schlema-Hartenstein mining districts border to each other and are forming together one deposit district of approx. 9 by 7 kilometres. Bismuth from Schneeberg sometimes appears in nice crystals, too.