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[Josele]

As seen in https://www.mineral-forum.com/message-board/viewtopic.php?p=40197#40197, scheelite specimens from Huanggang Mine (or, more general, Chifeng Prefecture, Inner Mongolia Autonomous Region, China) are sometimes treated to clean calcite matrix with an unexpected result of a change of scheelite color. In the related thread the color has turned to green. I wonder if my specimen has also been treated, because the brownish color is different to the whitish colors seen in Mindat gallery.
Has anyone seen this brownish color in other scheelite specimens from the Huanggang Mine?

[lluis]

Hi, Josele

As far as I remember, I think to have seen several specimens with this colour.
From very respected sellers.

So, I would think that yours is as is.

The green one, besides, has a very soft appearance, with edges that looks as polished to my eyes, not sharp as the ones your specimen has.

Anyway, seen more as yours.

With best wishes

Lluís

[Jordi Fabre]

It looks like slightly tinted due the etching process, but not so far of its real color, usually whitish, cream and some times bluish or grey-bluish by the Molybdenite inclusions.

As said in: https://www.mineral-forum.com/message-board/viewtopic.php?p=40197#40197 is easy to know it just cleaning them with super iron out or similar.

[GneissWare]

I agree. It looks like it needs a soak in Super Iron Out. It should go more grey.

[lluis]

By the way, I have seen in page placed by Josele that some are pinkish/violet.

Anyone knows reason?

With best wishes

Lluís

[Jordi Fabre]

[Josele]

In the reverse of this specimen can see a colorless core. I guess this a sign that it is not treated but anyway next monday I will buy any stain remover similar to Super Iron Out, which is not available in Spain.
Thanks to all for your help, on monday I will post the result after cleaning.

[lluis]

Hi, Jordi, Josele

I agree with the iron stained reason for Josele brownish color (for the piece, I mean).
I would try with Waller's solution, that is non acidic, or if you are in a hurry, with oxalic acid (cold solution!)
Anyway, I have searched, and scheelite dissolves in hot acid, so the green in some damages seems to be due to acid treatement, and non exactly in cold.... or room temperature.

For violet colour, I doubt in color centers (which are in the pink fluorites). I would think in a manganese maybe wolframate... (but with this colour, should be a Mn3+, that is not the most and stable thing.....Anyway, found in Rodhos, so....)

Pity that there is no study (pity for me, mainly; I doubt it would increase our knowledge too much, but.... :-) )

Many thanks!

Lluís

[Jordi Fabre]

[lluis]

Hi, Jordi

We had already had a talk (I think two years ago) on that.
That there is a part of color that is due to color centers, agreed (like the pink fluorites).
But all due to color center (except if there is a new definition, and all (cations, charge tranference, voids, distortions in net and all) are considered "centers of color), well... I would like to see the theory.

Anyway, a funky theory that the Greeks knew how to plate lead with a copper salt first and a silver salt later, or that the Romans could do electroplated tin denarii, had been in vogue. The first defended by at least some archaeologists, and referring to a fake slipped inside an Iitalian hoard of silver coins (the Parabita hoard; found and unrecorded properly I think at the beginning of 20th century or end of 19th century in Italia)

Anyway, we will see...

With best wishes

Lluís

[Josele]

Just to comment that finally I have decided to leave my scheelite specimen as it is.

As Super Iron Out is not available in Spain and even less in my small village, I found Dr Beckmann stain remover special for iron oxide, which I suppose is somewhat similar to SIO. But when I was ready to use it, I was thinking that if the brown color comes from iron oxide, it must be natural, so it is better to leave it like this. After all it's a nice honey color...

[GneissWare]

This is pretty typical color for Xuebaoding, and it already looks like it has been properly cleaned.