FMF - Friends of Minerals Forum, discussion and message board

[Roger Warin]

Hi Martin, Pete,
Thank you for this very interesting discussion.
Thank you for this beautiful drawing. Your best fitting is correct.
Here are three new pics.
I don’t think this is an abrasion that changes the face (?), but maybe it’s a stop of growth or a dissolution. Small crystal imperfections are aligned.
What do you think?
Roger.

[Pete Richards]

[Martin Rich]

Roger, thank you for the excellent photographs, so I can see some more clear!

My last drawing (the red one) has some faults. {100} does not occur. I made new Miller indices for each face and I'm not sure if the shape {011} occures.

As supposed, this rounded shapes could be from dissolving. In my opinion there are two points according to a dissolving matter. 1st: not all edges and corners are affected. 2nd: Roger's last two photos are showing on the faces interesting cavities.

Martin

[Roger Warin]

Hi Martin,
Many thanks for this fine work.
Here are two pictures highlighting the faces {010} and {0-10}.
I think the face {100} is present. I'll try to photograph. It is very small.
Roger.

[Pete Richards]

Until Roger's last two images I was uncomfortable with my understanding of the morphology and orientation of this crystal, but now I think I understand it. Attached is a SHAPE drawing with a different interpretation of the morphology from that of Martin. Roger, can you compare these drawings with your crystal and see if they seem correct?

One hint about the orientation of the crystal is that striations typically run parallel to the c-axis of euclase, another is that euclase has perfect cleavage parallel to {010}. Perhaps there are some minor cracks that reveal the direction of the cleavage?

[John S. White]

This is a fascinating discussion. To me it appears that all of the edges are abraded to some degree, so I am inclined to believe that this crystal spent part of its life in a sack with other pieces and abrasion of the edges was the result.

[Jordi Fabre]

[Martin Rich]

Good idea Pete, to make drawings with different Miller indices as mine. From a scientific point of few, a visual identification is some problematic but our drawings are giving a good imagination of the shape and habit of this crystal.

Abrasion or dissolving - thats the question.
In picture 2br981xx you can see a small cavity caused from a hit and some material chipped away. Why are not this edge and face affected (2c2r186x)? I my opinion the face with this small cavities is very interesting (4r200x). From dissolving? It would be interesting to see this cavities in an electron microscope. Roger, have you an electron microscope at home? My one is placed near the refrigerator but my neighbor says, that is a coffee machine. Hmm, I wonder why I can't get good results by my research of my minerals..... ;)
--- A lot of questions! ---

Martin

[Roger Warin]

Hi Pete, Martin, List,
Yes, this euclase specimen is interesting. But it is a bit small and some faces are difficult to discern.
Pete’s conclusion is excellent and the dihedral angles between the main faces corroborate.
If you look at the profile according to the b axis (the second Pete‘s drawing), we must admit that the four apexes are modified by very small faces. I emit an assumption of additional faces.
Another difficulty comes from a slight asymmetry growth, distorting precisely these faces of these tops.
No Martin, I do not have an electron microscope, but I have access to the laboratory of Mineralogy at the University of Liège (I am a retired chemist).
Warm thank you to Pete and Martin for helping me.
Roger.
PS: Here are two other photos.
The cavities are as negative of other parasitic lost crystals.

[Martin Rich]

Hello Roger!

I think your drawing shows a good conclusion of our efforts. I love such questions about crystallography and thank you for making so much photographs from this small xtl.

Martin

[Roger Warin]

Hi Martin,
It's really nice to encourage me. Many thanks.
I think Pete has summarized our thoughts. I found this sentence on Pete's Mindat page.
“I mourn the loss of awareness/knowledge of morphological crystallography among mineral collectors, geologists, mineralogists, and even practicing crystallographers. I find the shapes of crystals to be among the most elegant manifestations of the self-organizing principles of our world!”

It is obvious that the crystalline organization is one of the first examples of the organization of matter that ultimately by how much more complex processes, have led to life.
From a more pragmatic point of view, I really appreciate a good mineral that when I photographed its best profile and / or writing an article to describe it.
At the next essay ...
Roger.

[Roger Warin]

Here is another interesting euclase.
Colors are correct. One sometimes has enhancements of hues with modern lamps. It should work with a spectrophotometer to control everything.
Roger.