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EducationPOTD - superb talc crystals - obtained from the acidification of the sample?

23rd Apr 2024 03:58 UTCHerwig Pelckmans

Talc, Magnetite

Brosso Mine, Calea, Lessolo, Metropolitan City of Turin, Piedmont, Italy

see https://www.mindat.org/photo-1345712.html

and the child photo https://www.mindat.org/photo-1345713.html (shown above)

actual caption:

Beautiful clear green hexagonal crystal of talc obtained from the acidification of the sample.

According to sciencedirect.com:

Acidification is a natural process that usually occurs as a consequence of leaching of basic cations as well as nitrate in high-rainfall areas.

The caption sure makes it sound like these talc crystals were leached out by the collector... It would be interesting to know more about this "acidification".

23rd Apr 2024 04:32 UTCAlfredo Petrov Manager

You're right, Herwig. Indeed speakers of Latin-derived languages often use "acidified" to mean they used acid to etch insoluble crystals out of the matrix (usually a carbonate). To avoid confusion with natural acidification processes, it would be better to express it in English as "obtained by etching the sample with acid" - or some such similar expression.

23rd Apr 2024 07:56 UTCTimothy Greenland

Or simply "treatment of the specimen with acid". It would be nice to know which acid was used too...

23rd Apr 2024 09:32 UTCBen Grguric Expert

It appears some talc crystals occur in calcite at the locality. If that was the original matrix of the specimen discussed, then any weak acid, even vinegar could be used to expose the talc.

Talc is pretty resistant to acid attack, hence some laboratory benchtops were made from steatite.