FMF - Friends of Minerals Forum, discussion and message board

[Jordi Fabre]

We need some help. A small deposit in the north of Spain produces colorful green Pyromorphites. The funny thing is that they have a spectacular color change. They come out of the mine with a yellowish-greenish color and after a few hours under sun light their color changes to a deep green color. We discussed this phenomena in the Spanish Forum but no one there has a reasonable explanation so far other than the typical color centers, energy, etcetera...

What is the cause of this color change? Maybe someone here knows the answer?

Jordi

[Pete Modreski]

I don't think I've ever heard or read anything about the phenomenon of pyromorphite undergoing this type of color change; and a quick attempt at browsing the www and also GEOREF for this topic, did not term up anything about it. Interesting!

[Montanpark]

I have read somewhere (if i remember right an old article from 19th century) of colour change of pyromorphites of the Bad Ems area in Germany which came out almost colourless and turning into distinct brown when in daylight. Will try to find that reference and post. Kind of photooxidation maybe?

cheers
Roger

[Montanpark]

... found the (one short!) sentence today in the first issue of the "Emser Hefte" by R. Bode (german collector magazine, obsolete today and replaced by Mineralien-Magazin) , there the colour change is mentioned in the description of the Friedrichssegen pyromorphites .. will try to get the original references which are mentioned in the article.

[yowanni]

Thank you Roger,
We are waiting news :-)
Cheers,
Jonathan