Poudrette Quarry Behoite?

Originally I thought this specimen was ancylite, I suppose because of the pink color. Now I'm hoping for behoite. As I was photographing it I noticed the individual crystals in the sphere appeared to be terminated more wedge? shaped. It is sitting on calcite, the only associated mineral. It is so small and I am not yet an experienced photographer so this is my disclaimer why the photos are so poor (I need some excuse don't I?). I will include 3 photos. Hopefully between them someone can identify this specimen.

Thanks in advance for any help.

Jerry

Hi Jerrty,

Ancylite does sometimes come in spherical aggregates (possibly pseudomorphs) and the color might be OK. But the xls don't look like ancylite.
I also don't think it's behoite. (But I have seen very few of the ball type aggregates and some of your xls do look wedge shaped.)
It reminds me a bit (just a bit) of some of the platy rhodochrosite aggregates but the color is wrong.

So basically I pass on this one.

Modris



Edited 1 time(s). Last edit at 03/07/2013 03:04AM by Modris Baum.

Hi Modris,

I think it's really hard to tell only looking at the terminations. Again, I appreciate your taking the time to give your opinion. Have a good day!

Jerry

Hi Jerry,

After sleeping on it, I'm not so sure I can rule out behoite. Based on the very few behoites of the ball habit that I have seen, it seems to me that the aggregates are more "prickly" than what is shown in your photo. But this photo by Stephan Wolfsried does bear similarities to yours (if you squint just right):

Hi Modris,

I appreciate the second thought. I'm not sure I can squint just right, but maybe. Of course I would like it to be. Maybe someone with more experience with behoites will chime in.

Take care,

Jerry

Check it with a spectroscope ( I use one like this through the microscope [www.ebay.ca]) the difference will be obvious as Ancylite shows very strong absorption lines and behoite shows none.

Thanks Reiner, I've seen posts here on spectroscopes but haven't gone that far yet. Will there be some sort of scale with the scope so I'll know what to look for?

Jerry

Hi Jerry,

I think they come with an without scales. But all you really need is a "yes/no" response. If you see dark lines in the spectrum, you have REE.
In the case of ancylite-(Ce), the absorption actually comes from trace amounts of Nd (and sometimes other REEs) - not the Ce. So, in principle you couls have ancylite-(Ce) that shows no lines. But at MSH, Ce is pretty reliably accompanied by Nd. The most prominent absorption line is in the red/orange part of the spectrum.

In the case of -(Y) minerals, the lines are usually produced by one of the other REEs (I fortget which one). In my experience, the MSH -(Y) minerals don't always show significant absorption. If I remember, the strongest lines are in the green and blue (but there may be some in the red as well).

In general, it is harder to see the lines with dark/opaque specimens. If the sample is small, use a scope, focus on the sample, take out the eyepiece and "fiddle around" with the spectroscope near the tube. (I'm sure there is an optimal distance, but it doesn't really seem to be very critical). But, especially at high objective magnifications, make sure there is plenty of reflected light. If the sample is large, you don't even need to use a scope.

However, I really doubt that your sample is ancylite. And, in any case, the abosrption spectrum you see will rarely be distinctive enough - at least at MSH - to say more than 'yes/no" there is REE present.

Modris



Edited 1 time(s). Last edit at 03/08/2013 03:57PM by Modris Baum.

Hi Modris,

I appreciate the write-up. I really had no idea what to look for with a spectroscope. I agree that it's not likely to be ancylite, but the spectroscope should come in handy for other specimens.

What if there are two or more minerals with REE in the specimen? If you can isolate one at a time with the microscope will that do it?

Thanks again.

Jerry

I have a cheap monocular microscope which I use to focus on the crystal then I take the eyepiece out and slip a spectroscope into the tube
( adapted so it fits using rubber o-rings and tape) As long as you can fill the view with the crystal or material in question ( the limit is about 100X because at higher magnification the objective is so close I can't get enough light on it) you can test for absorption lines that indicate the presence of REEs. The lines ( black) will be obvious with ancylite. If there are no REEs you will see a complete color spectrum with no black lines.

Hi Jerry,

If you can isolate the two minerals sufficiently in the view, it will be OK. But in general, it's very hard to tell which mineral the absorption is coming from - at least in my experience. Note also that using the spectroscope to detect REE absoption is a different application than using the spectroscope for gemmology. I really don't know much about the latter, but it seems like a calibrated scale is important in that case. For REE detection you are just looking for a yes/no response. A calibrated scale miight make it clearer which trace elements you are seeing. But they are just that - trace elements. Not the "essentiual" elements in a mineral. Hence their relative abundances can vary widely without giving you a different mineral. On the other hand, detecting Nd (which is what usually happens) at MSH doesn't really tell you anything more than the mineral is likely Ce bearing.

Beautiful and unusual specimen, Jerry.

Does it do the usual ancylite color-change thing?

As long as you can fill the view with just one mineral at a time there is no problem with mixing up the spectrums. At a 100X this is not usually difficult to do. Also with a cheap spectroscope about the only absorption lines you will see are for Nd, Pr an Ho ( in the yellow to green bands)

I just checked my ball type Behoites. They are completely different. The shown ball looks like Chabasite to me. Similar ones are common in the Eifel area in Germany.
Or anther Zeolithe with similar symmetry? Gobbinsite?

Cheers Stephan

Thanks Reiner, that makes sense to me.

Jerry

Hi Modris,

I understand, thanks.

Jerry

Thanks Stephan, I'll do more checking in that area. I appreciate your checking.

Take care,

Jerry

I think it's a great crystal group too, Tim.

I'm not really sure what you mean about the color changing. I've seen it referred to here before. Is it supposed to look one color under one type of light and different in daylight? If so, it's too small for me to see in daylight.

Let me know.

Thanks.

Hi Jerry,

If you have an ordinary desk lamp, just change the bulb from tungsten to compact fluorescent and use that to illuminate the specimen under the scope. For bigger stuff (doesn't have to be very big), just wave it back and forth between a tungsten bulb and fluorescent (any kind).

Regarding Stephan's suggestion: My first reaction was actually gmelinite or chabazite as well, But - for MSH - the color is just wrong. Gmelinite does come in yellow, orange, reddish, greenish, white, black, colorless here - but I have never seen pink/violet. (In fact - unless it's an artifact - the color seems too intense for behoite as well.)

Modris

An afterthought: I have seen faintly pinkish platy chabazite balls (from the Poudrette pegmatite area).. Is the color in the photo perhaps too saturated? Do you know what environment your specimen is from?



Edited 2 time(s). Last edit at 03/09/2013 07:28PM by Modris Baum.

Hi Modris,

Thanks for the tungsten/fluorescent advice. I get it now.

No I don't know the environment.

I'm embarrassed to admit that the color is not correct. I was so concerned with getting a sharp picture (which I didn't) that I paid no attention to the color. The third photo is the closest to the right color, but really it appears light pink under the scope. It's sounding more and more like chabazite.

I apologize to all those who made the effort to help me. I know how hard it is to try to identify something in person, much more so in a photo and close to impossible in a bad photo. I'll do my best to be more careful in the future.

Thanks to all.

Jerry



Edited 1 time(s). Last edit at 03/10/2013 02:05AM by Jerry Cone.