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PhotosLatrappite - Oka complex, Oka, Deux-Montagnes RCM, Laurentides, Québec, Canada

28th May 2015 15:21 UTCRichard Gunter Expert

Perovskite Supergroup, Calcite

Oka complex, Deux-Montagnes RCM, Laurentides, Québec, Canada

Is this Latrappite or a Perovskite Group mineral? There is not enough in the photo to be able to distinguish the two if it has not been confirmed as Latrappite.

28th May 2015 15:51 UTCRob Woodside 🌟 Manager

Without analysis it is a Perovskite group mineral. Message sent.

30th May 2015 10:29 UTCAntonio Zordan Expert

Ciao Richard and Rob

I obtained this tumbnail size specimen in mid '80 and retain the original label, from Monteregian Minerals, referring these data: Misc. 86, Latrappite from Oka, Que; moreover the stick-on box label shows "Niobium pit".

As I repute L. Horvath undoubedtly a trustworthy person I did't consider necessary to test by XRD or SEM-EDS. You need to delete the photo?

Sorry for my English.

Antonio

30th May 2015 15:44 UTCTony Peterson Expert

Antonio - your English is more than adequate! No apologies necessary.

As far as I can tell, none of the lattrapite photos is accompanied by an analysis, or is captioned as "identity confirmed". I have seen a lot of perovskite in rocks, and have quite a bit in my collection, and these lattrapites are quite distinctive for being extremely sharp-edged and with a very even pseudocubic habit. Antonio's specimen looks just like the others, so picking on his photo seems unfair.

But, it makes me think that I should get an analysis of my own to be on the safe side. What Na/Ca and Nb/Ti ratios are needed to define lattrapite?

Tony

30th May 2015 15:48 UTCRichard Gunter Expert

Hi Antonio:

It is not necessary to delete the photo, just change the title to Perovskite Group instead. Oka has both Latrappite and Niobian Perovskite in almost identical crystals. The Niobium Pit is one of the areas for both Latrappite and Niobian Perovskite. There is abundant literature on the Oka Complex and the characterization of Latrappite that can be accessed on the RRUFF site should you want to read further. I have no problems with Laszlo's identifications but in this case it is almost impossible to determine Latrappite without analysis.

30th May 2015 15:57 UTCRichard Gunter Expert

Hi Tony:

Your post came in as I was composing mine for Antonio. I asked about Antonio's photo as it was posted in the daily photos and I thought it should be changed. You are correct about there being other photos in the Latrappite post that might be more properly be Perovskite Group.

Latrappite in the Nb analogue of Perovskite so it must be Nb dominant. It is normally Ca dominate. Check the characterization paper for Latrappite for the chemistry involved

I have found that the true Latrappite are not perfect cubes but have a notch on one side of the face. There is probably not enough data to confirm that.

30th May 2015 21:50 UTCTony Peterson Expert

Yes, an analysis does seem worthwhile. I'll try to post a spectrum soon.

Tony

31st May 2015 13:48 UTCAntonio Zordan Expert

Ciao Friends

I just do the change.

Thanks for this and next advices.

Antonio

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