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Identity HelpGive me a tip please...

12th Aug 2007 18:53 UTCGábor Mesics Expert

I have not found any locality reference, and without this I cannot identify this specimen.

The details:

- Locality: Kistárkánypuszta, Hungary. An abandoned bauxite mine in limestone, rich in sulphides (pyrite, marcasite). Other identified minerals: calcite, goethite,gypsum.

I have found the specimen on surface of waste dump.

The questionable mineral is pale greenish-creamy-yellow, hexagonal (pseudohexagonal), grown on goethite, near pyrite crystals.

If anybody have a good tip, please reply.

13th Aug 2007 08:34 UTCPeter Haas Expert

Looks like altered mica, so-called "sericite".

13th Aug 2007 10:54 UTCUwe Kolitsch Manager

Yes, very probably an altered layer silicate.

13th Aug 2007 18:48 UTCŁukasz Kruszewski Expert

It looks a bit like pyroaurite-sjoegrenite mineral group. Possibly fougerite? (its structure is layered with brucite-type layers).


Greetings!

14th Aug 2007 08:46 UTCPeter Haas Expert

The colour is wrong for fougerite; while it is greenish when fresh, it decomposes almost instantaneously into lepidocrocite/goethite upon exposure to atmospheric oxygen.

16th Aug 2007 18:56 UTCGábor Mesics Expert

Many thanks for the tips, but for me very hard to believe , that it is a mica.

This place hase full sedimentary origin, only limestone, and fine-grained bauxite. My first mind was, that it must be a secondary, hydrated iron sulphate, like copiapite, or coquimbite.

Sulphates are not rare minerals on the nearly places, like Nyirád Mine (mindat.org/loc-27124.html),is about 10 km from this location.

I attached an other photo wich shows an other form of this mineral, maybe this helps (or not)...

17th Aug 2007 10:00 UTCUwe Kolitsch Manager

Such minerals can form at very low T.

Have you checked solubility in water and acid(s)?

18th Aug 2007 02:52 UTCRobert Knox

I don't know if this will be of any help, but I ran across this photo from one of the vendors that advertise on mindat. The location may/maynot be correct as well as the mineral. Segnitite! It sure looks a lot like what I see in your photo, better that the segnitite photos in mindat.


Bob

18th Aug 2007 11:18 UTCUwe Kolitsch Manager

Segnitite or other members of the alunite supergroup can be excluded.
 
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