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Identity HelpShattuckite vs. plancheite

28th Mar 2009 20:25 UTCRolf Brandt

Has anybody suggestions how to distinguish between shattuckite and planchite in a hand specimen? Looking through all the Mindat pictures does not help a lot.

28th Mar 2009 23:06 UTCDebbie Woolf Manager

Hi Rolf,

How about a hardness test, plancheite is 6 whereas shattuckite is 3½

Best Wishes

Debbie

29th Mar 2009 07:20 UTCRolf Brandt

Hi Debbie,

I know, but i am looking for something less destructive. The specimen are often quite fragile, scratching it would damage them. Of all these pictures, i wonder how people know, what is what. Regards Rolf

29th Mar 2009 07:24 UTCRolf Brandt

Sorry, i was to add, that probably the darker-blue-ones are shattuckite, but some light blue ones are also in that category.

29th Mar 2009 17:28 UTCUwe Kolitsch Manager

Plancheite and shattuckite are visually often very similar and best identified by analytical methods (e.g., XRD).

Not all specimens on the market are labeled correctly.

29th Mar 2009 23:36 UTCDebbie Woolf Manager

Rolf, any pictures of the specimen & where's it from ?

30th Mar 2009 19:39 UTCRolf Brandt

HI, YES 2 PICTURES. BOTH SPECIMENS ARE FROM THE CONGO.

31st Mar 2009 21:30 UTCGerhard Niklasch Expert

I wonder just how much is really known about the conditions which might favour one or the other species to be formed, and possible deductions based on what associates are present?

E.g. by composition alone, I'd naively imagine that Shattuckite would be preferred when excess SiO₂ is available, some of which might finally end up as a layer of secondary quartz on top. (But this is speculation on my part.)

Trawling Google Scholar did not come up with much. Evans&Mrose 1977 suggest that density and refractive index (if you can measure them precisely enough) might tell them apart.

1st Apr 2009 16:40 UTCPaul De Bondt Manager

Hi,

Rolf,in my eyes, or as I see them on my screen, are Plancheite. The first seems to be from Mashamba, the second is more a Kambove piece.

The difference between P and S is very difficult to say. But one thing is in most cases true, S is in darker than P. Nevertheless, sometimes pale minerals we tought to be P, turned out to be S and vise versa. :S

Not an easy subject. Analisis, like mentionned above are mosly required to distinguish them.

As for Bisbeeite, it has, to my knowledge, never been identified from Katanga. It is here a plumose variety of Plancheite.

I hope this helps.

Take care and best regards.

Paul.

1st Apr 2009 17:10 UTCRoger Van Dooren

I agree with P Debondt explanation; I have had many spec of both minerals. The best ones come from Tantara. Often, P is more fibrous, S massive or pseudomorph after calcite but ther is not definitive identification.

Roger

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