FMF - Friends of Minerals Forum, discussion and message board

[MrOHBrown]

I recently acquired a beautiful FeAsS specimen.

I love that formula.

I read that it can tarnish, how might I avoid this?

Many thanks.

[Jordi Fabre]

The Arsenopyrite tends to tarnish, some times slowly some times faster, depending different circumstances. If the whole specimen is Arsenopyrite then it will tarnish faster than if the matrix contains carbonates, if the specimen was treated with acid to delete covering minerals then it will tarnish really fast, and if you display the specimen under day light and you live on a place with high humidity, close the sea for example, also it will tarnish faster. So to avoid it, if you buy an Arsenopyrite with related carbonates, not previously treated with acid and you protect it of the light and humidity, then probably the tarnishing will occur so slowly that you neither will see it

Hopefully it helps,

Jordi

[Pete Modreski]

I was wondering about this, because I did not think that arsenopyrite tarnishes very much, if at all. Perhaps it is our dry climate here (Colorado). I have some specimens of the bright, shiny, large crystals from China, and I have not expected that they would tarnish at all; though the specimens I am thinking of, I must admit I have not had for very long.

Pete

[Jon Mommers]

In addition to what Pete and Jordi wrote, I have found that if Arsenopyrite is stored in the same draws as Native Sulfur or Marcasite then they do tend to tarnish more quickly. Also if the specimens have been cleaned with products like "Tarnoff" or similiar liquid polishes they will darken over a relatively short time.........several months to a year.

Arsenopyrite is a great mineral to collect and has some wonderful associations

Cheers

Jon

[Jordi Fabre]

Correct Pete, the process could be very slow, and you have some good features: Chinese Arsenopyrites are very shiny, usually them are not acid treated, them appears frequently with carbonates around, you live on a dry place and I assume that your specimens are protected of sun light.

When I saw or buy very old collections, all Arsenopyrites tarnished more or less, but, again, the process it could be extremely slow.

Jordi