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PhotosMeionite - Grenville Scapolite Prospect, Grenville-sur-la-Rouge, Argenteuil RCM, Laurentides, Québec, Canada

23rd Nov 2013 16:09 UTCPhil M. Belley Expert

Meionite

Bancroft area, Ontario, Canada

The locality on the label is Bancroft. Grenville should not be assumed. Fluorescent scapolite is far more common in the Central Metasedimentary Belt than people think. The sample looks like it may have graphite or phlogopite? I never saw either mineral in material from Grenville.

23rd Nov 2013 17:38 UTCMatt Neuzil Expert

I almost think the photo looks like nepheline and Phil, like you said graphite. Perhaps it is scapolite though. Just my thoughts

23rd Nov 2013 19:01 UTCReiner Mielke Expert

Looks like typical stuff from Quebec. Is all the scapolite from that locality Meionite?

23rd Nov 2013 21:06 UTCPhil M. Belley Expert

There are at least 2, perhaps 3 localities in Grenville and 1 locality near Otter Lake that I know of. I have never seen graphite in any of the samples from these locations. I have not seen chemical analyses for the scapolites. I am assuming this one shows the characteristic bright LW-UV fluorescence, which is why it was put in Grenville.

Changing a locality from a sample label is risky and in this case should not be done. Who's to say that a collector didn't find fluorescent scapolite near Bancroft? We have no way to know. If the label is wrong, where is the fluorescent scapolite from? Grenville? Otter Lake? Baffin Island? Afghanistan? An unknown locality?

With rare exceptions (highly unique samples), once locality information is lost, it's lost for good.

24th Nov 2013 00:54 UTCRob Woodside 🌟 Manager

I don't recognize any obvious graphite in the photo and the white greeny looks like Greenland sodalite. If it was it should darken under UV.

24th Nov 2013 11:38 UTCVik Vanrusselt Expert

Hello all,

- the greenish grey parts of the specimen show the yellow (with an orange tinge) fluorescence under LW UV, which the Grenville locality is known for.

- associated minerals are pyrite and unknown (to me at least) brown mineral which seems to have a conchoidal fracture (smoky quartz?).

I do not believe it to be either Phlogopite (always platy crystals?) or Graphite (never brown?).

- http://www.mindat.org/loc-224159.html: "There is no official designation of a “Bancroft area”, or district, that has any relevance here. It has different definitions, and highly variable boundaries, depending who you ask." → Not really an 'exact' locality, is it?

- The only other specimen I (used to) have that came close to this particular one, had the "Otter Lake" occurrence on the label, but this was questioned by the Mindat administrators and subsequently changed to the Grenville scapolite occurrence.

- So, I just thought I'd avoid any dispute about the Bancroft locality and uploaded the specimen to Grenville.

- I do not know whether it is true Meionite or the Meionite-Marialite Series (a.k.a. 'Scapolite). I would probably have to have it analysed, but this would cost more than the specimen is worth.

Vik

24th Nov 2013 13:12 UTCPhil M. Belley Expert

associated minerals are pyrite and unknown (to me at least) brown mineral which seems to have a conchoidal fracture

Perhaps titanite.

I would consider the locality "lost." It would not be prudent to attribute the sample to the Grenville prospect.

24th Nov 2013 14:09 UTCReiner Mielke Expert

While on this subject is there actually a locality for scapolite of this type ( wernerite) in the bancroft area? and if so where? As far as I know all of it comes from the locality Vik has attributed it to.

24th Nov 2013 15:07 UTCDonald Doell Expert

Scapolite (probably marialite) occurs at the Saint Sauveur Graphite Prospect. It is associated with graphite (sometimes in spheres), titanite, pyrrhotite, phlogopite, grossular, vesuvianite, apatite, diopside, zircon (purple), wollastonite and a tourmaline (probably dravite). It fluoresces very much orange rather than yellow. It is not all fluorescent. Having given away a bunch of this material last year it is possible some people have acquired some of it. I essentially gave away ALL of my fluorescent orange scapolite from this locality to Charles Gould. The orange color can be very intense, but inconsistent throughout the scapolite. It is can perhaps be distinguished from other Canadian Scapolite which usually fluoresces yellow. The marialite versus meionite for this material is only based on Raman, which may be inaccurate to make this distinction.

24th Nov 2013 17:08 UTCReiner Mielke Expert

Hello Donald,

Is it orange under long wave or short?

28th Nov 2013 02:46 UTCDonald Doell Expert

It is orange under both.

28th Nov 2013 16:05 UTCRichard Gunter Expert

Hi Donald:

The Meionite from Grand Forks British Columbia, seen as acicular colourless crystals in Anorthite, also has strong orange SW and LW UV fluorescence. The Meionite has been determined by XRD. I wonder if the fluorescent colour in the Scapolite Group is tied to composition?

28th Nov 2013 19:58 UTCPhil M. Belley Expert

I wonder if the fluorescent colour in the Scapolite Group is tied to composition?

It is caused by the presence of S^2- substituting for SO₄^2-.

As for the locality, feel free to attribute any locality you wish, but this is not scientifically reliable and can result in incorrect locality info being passed along. Fluorescent scapolite is not so uncommon, especially in the Grenville. Once locality info is separated from a specimen, it can never be surely determined (unless, of course, it is very unique like Sweet Home rhodochrosite on matrix or mushroom habit red elbaite)

28th Nov 2013 20:14 UTCReiner Mielke Expert

Could the S content ( or some other minor element) be unique to a given locality? Is anyone know of a study of scapolite compositional variation for a specific locality in the Grenville? There seems to be quite a variation between different localities in general see: http://rruff.info/doclib/cm/vol6/CM6_670.pdf

29th Nov 2013 02:08 UTCMatt Neuzil Expert

It makes sense since isn't fluorescence in sodalite related to sulfur ?

29th Nov 2013 12:39 UTCPhil M. Belley Expert

Matt, you are correct. S^2- is responsible for fluorescence in sodalite as well.

Reiner: I suppose there could be differences in composition as long as enough S^2- is present to result in fluorescence, but I have not seen any analytical data.

29th Nov 2013 23:27 UTCRichard Gunter Expert

Is it possible the fluorescent Scapolite has a slightly different genesis than the non-fluorescent type? The Grenville Province calcareous metasediments have abundant Scapolite in regionally metamorphosed carbonate sediments according to Dr. Shaw (Am Min) but almost none of it is fluorescent. The Grand Forks, British Columbia fluorescent Meionite is part of a calcareous skarn deposit (spinel etc.) and occurs directly with Anorthite; an association not found in the regionally metamorphosed carbonates.

11th Jul 2014 00:41 UTCRob Woodside 🌟 Manager

Going after Fluorescence, and colours generally, with this lot requires spectroscopy as amounts below detection (EMPA) are often responsible. Further probing will give you the elements, if you are lucky, but not the molecules that give the colours. For instance the yellow S^-2 fluorescence of scapolite and sodalite results from vibrations of the two sulfur atoms in S^-2. Detection of S^-2 requires spectroscopy where quantitative results are very hard to obtain.

12th Jul 2014 22:33 UTCVik Vanrusselt Expert

Hello all,

which of the mentioned localities in the comments above should I attribute my specimen to eventually?

For now, I've changed it to the "Bancroft area" locality http://www.mindat.org/loc-224159.html

Let me know if this is more correct than the Grenville locality or not.

Vik

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