Tremolite : ☐{Ca2}{Mg5}(Si8O22)(OH)2

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Copyright © SMS 2010
minID: JGP-VP6

Tremolite : ☐{Ca2}{Mg5}(Si8O22)(OH)2

Copyright © SMS 2010  - This image is copyrighted. Unauthorized reproduction prohibited.

Note: Tremolite is not listed in our database for this locality. This specimen may be misidentified or the mindat list of rocks and minerals at this locality may be incomplete.

Field of View: 3 mm

Pale green tremolite in calcite from Bird's Creek, Bancroft District. This specimen came from a collection of unmounted microminerals I recently obtained. FOV is about 3 mm in length. I originally called it diopside, but further dialogue with Mindat members and an EDS analysis I commissioned leads me to change the ID to tremolite. See this link:

Photo and specimen: Steve Stuart.

This photo has been shown 334 times
Photo added:13th Jul 2010
Dimensions:800x614px (0.49 megapixels)
Date/Time of Photo:11th Jul 2010 23:08:03
Software:Picasa 3.0
Exposure time:1/51s
Focal Length:24mm
ISO speed:231
View Steve Stuart's Photos View Tremolite Gallery

Discuss this Photo

PhotosDiopside - McFall Lake occurrence, Herschel Township, Hastings Co., Ontario, Canada

15th Dec 2016 14:02 UTCTim Jokela Jr

I'd suggest that this is more likely tremolite. Striae and termination are wrong for diopside. 5 photos total.

15th Dec 2016 14:10 UTCReiner Mielke Expert

I agree does not look like diopside rather tremolite.

15th Dec 2016 14:56 UTCUwe Kolitsch Manager

A message had already been sent in 2010 by Rob.


15th Dec 2016 18:50 UTCReiner Mielke Expert

Good catch Uwe now that I look at it more closely that also does not look like diopside to me rather tremolite. This is what the diopside from there should look like: http://www.mindat.org/photo-188603.html

15th Dec 2016 21:15 UTCSteve Stuart Expert

A few points:

1.) Tremolite is not listed as found at this locality. A look at the gallery of diopside specimens from this locality implies that it has been collected there since at least 1964. So, no one has seen tremolite in over 50 years of collecting? Until now?! I have a few samples of this stuff, all called diopside, with stout bladed green habit, some striated. Since Mindat does not give tremolite as an option at this locality for this green mineral, calling it diopside did not seem out of line.

2.) What testing would be needed to distinguish diopside from tremolite? A quick look at the formulae would imply that simple EDS, as supplied by Kerry Day for example, would not be enough. Both species are mostly Ca, Mg, Si and O. Perhaps someone well-versed in analysis of the spectra could tease out a definite ID through relative peak magnitudes. If Reiner or Uwe think that EDS would be helpful, I'll send a piece off to Mr. Day.



15th Dec 2016 21:24 UTCErik Vercammen Expert

Is it possible to see a cross-section of the cristal, to see if it is a pyroxene (square) or amphibole (hexagon or diamond)?

15th Dec 2016 21:33 UTCReiner Mielke Expert

There is no reason that tremolite could not be found there and the list may not be complete. How it fractures is the best way to tell. Tremolite breaks into splinters and diopside does not.

15th Dec 2016 21:35 UTCReiner Mielke Expert

Also as Erik says the cross-section should tell if you don't have any to spare.

16th Dec 2016 01:21 UTCKeith Compton Manager


I note that the late Ann P.Sabina's publication on the area only discusses Diopside from here. There are other localities for tremolite in her publication.

see: (1986), Rocks and Minerals for the Collector, Bancroft-Parry Sound Area and Southern Ontario. GSC Misc. Report 39

The photo in question appears to have a "brother/sister" from a different angle in the same owner gallery.

I certainly couldn't say one way or the other.



16th Dec 2016 02:01 UTCSteve Stuart Expert



Here is Mindat specimen # TVX-57V, with its cross-section. Opinions?

16th Dec 2016 02:07 UTCSteve Stuart Expert



Mindat specimen # 3HV-GY7 and its cross-section. Seems more square than the previuous one. Both are on my micromineral specimen, MM 551.

16th Dec 2016 02:09 UTCSteve Stuart Expert



Last one- Mindat specimen # 3RL-K4A and its cross-section.

16th Dec 2016 02:11 UTCSteve Stuart Expert

I was not able to find the specimen that Tim Jokela used to begin this thread. I'll keep looking!

17th Dec 2016 01:37 UTCTim Jokela Jr

Should get it analyzed. Vast amounts of interesting microminerals are not listed by Sabina or here.

The striae, habit, and x-section are wrong for diopside.

For comparison, specimens from the Grace Lake roadcut often show the two together.

I'm not trying to insult anybody by pointing out problem ID's, just trying to make a few corrections.

I don't pretend to know it all, and am happy to be proven wrong by analytical work or more experienced collectors.

17th Dec 2016 01:40 UTCReiner Mielke Expert

They look like typical tremolite crystals.

17th Dec 2016 12:07 UTCUwe Kolitsch Manager

Cross-section of 1-MM551cross-section2016-12-15-20.45.39ZSDMap.jpg reminds more of diopside.

Not sure about the others, although I'd also lean towards tremolite.

17th Dec 2016 12:54 UTCReiner Mielke Expert

1-MM551 is very much like the actinolite from this occurence. http://www.mindat.org/loc-219580.html In fact I have seen samples from there almost identical to 1-MM551. Although it is called actinolite ( a historic name not backed by analysis) it is likely tremolite. I currently have a sample of this material out for testing to determine if it is actinolite or not.

17th Dec 2016 14:03 UTCFrank Craig

Actually, EDS can be used to distiguish between the amphiboles and pyroxenes. But I agree - looks more like an amphibole than a pyroxene.



17th Dec 2016 16:05 UTCReiner Mielke Expert

Thanks Craig!

17th Dec 2016 17:22 UTCSteve Stuart Expert

I'll extract a sample from its calcite matrix and send it out for EDS analysis.

13th Jan 2017 02:10 UTCSteve Stuart Expert

Sent a sample to Kerry Day in Ottawa. He calls it tremolite. See attached spectrum.

13th Jan 2017 02:42 UTCReiner Mielke Expert

Looks exaclty like the tremolite from here: http://www.mindat.org/loc-219580.html

13th Jan 2017 03:37 UTCSteve Stuart Expert

My lingering issue is that my spectrum more closely matches the diopside spectrum posted by Frank Craig, especially the relative heights of the Mg, Si and Ca peaks, as well as the discernible Fe peak.

13th Jan 2017 10:55 UTCReiner Mielke Expert

Maybe Frank's equipment can distinguish diopside from tremolite but not Kerry's. To those familiar with tremolite and diopside from the Grenville the difference in appearance is obvious. Your stuff is tremolite. Of course if you still have doubts XRD will clearly distinguish the two and John Attard will do that for you for $50. However if you look at a small fragment of your unknown and compare it to a small fragment of known tremolite and diopside the difference will be obvious.

13th Jan 2017 14:03 UTCAndrew Debnam

I would agree with Reiner, I have collected Tremolite and Diopside from many localities in the Bancroft area over the last thirty years and these samples with a high degree of conviction are tremolite





Happy New year

13th Jan 2017 15:13 UTCFrank Craig

Hi Steve:

Unfortunately, you can't make a qualitative comparison between spectra obtained on different systems - each display data diferently (see below). Kerry also included a spectrum from a known (I presume) tremolite produced on his system. That matches the unknown you submitted - so I am comfortable with a call of tremolite based on spectrum appearance (CaO Wt% [even semi-quant] would be even better, but...)

These spectra were normalized to the Si Peak

13th Jan 2017 15:17 UTCFrank Craig

BTW - I forgot to mention that each of the spectra in the figure were generated from not only the same sample, but the same particle.

13th Jan 2017 15:42 UTCMatt Neuzil Expert

I think the pictures of diopside for the local say a lot as well. In the mineralogy lab where i studied, there was a large piece from mcfall lake. I dont believe there was a label. It had to have weighed 80 pounds or more. Was chock full of the typical diopside there. I think the only other mineral i saw accompanying xls was mica. All in standard calcite matrix for the place.
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