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Identity HelpJarosite or Hydroniumjarosite ????

24th Aug 2016 02:54 UTCChristopher O'Neill

Hello all,

Is this specimen (from Chuquicamata District, Calama, El Loa Province, Chile) Jarosite or Hydroniumjarosite?

Looks similar to Jarosite from Modum, Norway http://www.mindat.org/photo-159118.html

Looks similar to Hydroniumjarosite from France http://www.mindat.org/photo-578956.html

Thank you,

Chris

24th Aug 2016 06:14 UTCAlfredo Petrov Manager

Doesn't matter what it "looks similar to", as those 2 species can not be visually distinguished. You'd need an accurate measurement of potassium and sodium content (your normal SEM/EDS probably won't be sufficient, especially if the sample is not anwhere close to endmember composition, and you need a pure sample, which is difficult to separate out with certainty in fine-grained material. Sorry to sound like a party pooper, but sometimes we're better off using group names and labelling it Jarosite Group. Nothing wrong with using group names on labels; we should encourage it more often. (Species collectors hate me, I know. :-( )

24th Aug 2016 08:51 UTCUwe Kolitsch Manager

Alfredo is totally right. Such aggregates can also be composed of mechanical mixtures of different jarosite-group minerals.

24th Aug 2016 10:23 UTCPavel Kartashov Manager

Moreover, "Jarosite from Modum, Norway http://www.mindat.org/photo-159118.html" is rather usual natrojarosite, than real K-dominant jarosite. I also don't belive, that "Hydroniumjarosite from France http://www.mindat.org/photo-578956.html" is really Hydronium- in a whole its mass.

And, of course, this sample from Chuquicamata also is natrojarosite with 99.95% of probability.

"Looks similar to photo ID" is very strong argument when you have mineral, single crystals of which are usually zonal and sectorial. :-D:-D:-D

24th Aug 2016 12:13 UTCLefteris Rantos Expert

Absolutely impossible to tell apart. Very similar compact straw-like columnar masses commonly found in different localities within the Lavrion District in Greece (locally known as "Carphosiderite") have been shown to contain Jarosite, Natrojarosite, Hydronium-Jarosite, Plumbojarosite and even Argentojarosite components in widely variable ratios, even if the specimens look identical. Of course Jarosite and especially Natrojarosite (depending on the deposit) are much more likely than anything else.

24th Aug 2016 21:44 UTCChristopher O'Neill

Thanks everyone, for your input.

I will take Alfredo's suggestion and post under Jarosite Group.

Regards,

Chris

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