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Identity HelpZeunerite/metaZeunerite?

10th Aug 2010 14:12 UTCGeorge Eric Stanley Curtis

I have recently found some examples of Zeunerite (?) metazeunerite in freshly opened cavities in a dump rock.

I am aware that Zeunerite converts to metazeunerite, but understand this takes years.

To be safe I have listed my newly-found crystals as MetaZeunerite, but wonder if there was any easy way to know which was which?

If I find a crystal INSIDE a lump of freshly broken dump rock, would that be Zeunerite or metaZeunerite?

I notice that Mindat has many pictures of both, but if all collected crystals turn to metaZeunerite, how are there so many non-meta pictured?

I have no axe to grind here, I am just curious.

The same question would apply to Torbernite I guess.

Regards

Eric B)

10th Aug 2010 15:31 UTCUwe Kolitsch Manager

"If I find a crystal INSIDE a lump of freshly broken dump rock, would that be Zeunerite or metaZeunerite?"

Depends on the temperature at which the crystal has formed, and on the temperature to which is has been subjected later on.

10th Aug 2010 18:05 UTCGeorge Eric Stanley Curtis

Thanks Uwe,

Temperatures are completely unknown, except they were probably within the normal ambient range whatever that is.

(-10C in winter, +25C in summer?)

In short, there is no way of accurately knowing the temperature history.

Are there no visual clues?

I mean, if you look on the mindat galleries, there are an awful lot of both, I thought maybe there was some way of knowing.

Thanks anyway,

Regards

Eric

B)

10th Aug 2010 18:37 UTCUwe Kolitsch Manager

"Are there no visual clues?"

From my personal experience (XRD analyses) on both (meta-)torbernite and (meta-)zeunerite:

Transparent crystals can be both meta- and normal forms, opaque crystals are almost always the meta-form.

10th Aug 2010 19:19 UTCReiner Mielke Expert

Does it really matter? If it isn't meta now it eventually will be.

10th Aug 2010 20:46 UTCGeorge Eric Stanley Curtis

\thanks for all,

No Reiner, it doesn't matter to me, I was just curious.

I wondered how people knew the difference when posting on mindat, is all.

I am happy to accept it is all meta.

Cheers,

Eric.

11th Aug 2010 09:40 UTCRock Currier Expert

George,

The answer is that people almost always don't know. I think the observation of Uwe based on his x-ray experience is about as good as you are going to get, baring an x-ray analysis of samples from some of the specimens you found. When you look at the pictures on the gallery you have to assume that in most cases, the person who wrote the caption didn't know for sure that they had used the correct species name. Also you can be sure that the conversion to the meta form is not quick in most instances but gradual and it is quite possible that both minerals are present in most crystals. Uwe's observation that the opaque crystals are almost always the meta form is as good as you can get. Most people including myself, a money grubbing specimen dealer, usually take the liberty of calling the transparent forms or mostly transparent forms Torbernite or Zeunerite. But as Uwe points out that this is certainly not an good way to make the distinction. I would suppose that there are many other minerals in the same boat as these. Does anyone know of any studies where the conversion temperatures to the meta forms have been studied and the conversion rate of this kind of change vs. temperature? I don't know of any, but than I do not spend a lot of time reading scientific literature.

11th Aug 2010 11:32 UTCGeorge Eric Stanley Curtis

Thanks Rock, and all of you.

I am enlightened.

Mine are a mix of transparent and opaque - but that means not a lot.

Regards

Eric B)

11th Aug 2010 15:50 UTCTimothy Greenland

I generally label mine (meta)Torbernite or (meta)Zeunerite for the collection labels and catalogue...

Cheers

Tim

11th Aug 2010 16:22 UTCJolyon Ralph Founder

Personally, I'd just label them torbernite or zeunerite if you don't know what the hydration state is. In the grand scale of things it's pretty unimportant.

Jolyon

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