White fibers on metallic mineral

Perhaps someone would be able to help me identify this piece? I found it at the copper, lead and silver mine Grube Adolf-Helene, Altlay, Zell, Hunsrück, Rheinland-Pfalz, Germany (http://www.mindat.org/loc.php?loc=21809) in 2006. It is a piece of quartz with some brown veins and measures 2,4 cm. I collected it because it had a 7 mm silvery metallic area. When I got home I placed it in a cardboard box and didn’t look at it for about two years. Then I had another look at it, and to my amazement saw, that the silvery area was now almost completely covered by the white curved fibers, that you see in the photo. The fibers are up to ca. 3 mm in length and quite fragile as you can imagine. The tips of some of them are light brown. I know that the photos are not perfect, but perhaps they are good enough to identify the white fibers and the metallic mineral from which they grew?

Thanks in advance,
David

Looks like pharmacolite or picropharmacolite on rotting Arsenopyrite??? I can't see the metallic.

Probably an iron/metal sulphate growing from an iron sulphide (and/or other metal sulphide) inclusion.

Looks like halotrichite to me.

Hello,

Some iron sulphate, halotrichite or maybe siderotile or hexahydrite. Relatively common in Germany, if you collect marcasite or pyrite ores.

Regards,
Sebastian Möller

Of course!!! A sulfate like halotrichite is more common than an arsenate.

Thanks for your help. I would not have got this far without it. The post collecting growth really surprised me, but I assume it is not that uncommon after all.

David

Hello,

I had once a specimen from Helgoland, being pyrite/marcasite and have been in the salty water of the NOrthern Sea. When I found it, it had been at the beach. It stayed together and shiny a few month and after half a year in the garage...surprise! Fibers of melanterite up to 2 cm grown in the middle of the specimen, having cracked it in a half.

I have many different specimen from several pyrite/quarz localities in the German Black Forest, especially antimony mines, being covered with specimen like halotrichite/siderotile, melanterite and copiapite, even römerite from Clara mine has formed in my collection.

...so, not uncommon. Take any wet sample of fine-grained marcasite and let it as it is in a humid environment (garage, cellar, even rooms) for half a year and be surprised what you will get.

Regards,
Sebastian Möller

I seem to have had the same thing happen to one of my pyrite/marcasite specimens in about a weeks time.
So I took pictures of it, ... but .. 2 weeks later they were gone :( where did they go ?


these are what I ' did ' have









Wayne Corwin

The new formed sulphates are also not very stabile: they may be hygroscopic, and capture moist from the air. They can partly dissolve, the iron can oxidize further so that new compounds are formed etc.