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There appears to be a third particularity - it's habit.
I've looked through Goldschmidt and in other places and found no report of a large 001 face with adjoining 321 faces. In fact, there is no dis ...

There is a great mineral society in Baltimore with several members who have collected extensively locally. I'm sure they will be of help.
It's the Baltimore, Maryland Chesapeake Bay Mineral Society
...

I found the names:
Daniel Atencio at the University of Sao Paulo and Ricardo Scholz at the University of Duropraiso. If they can't do analyses, they can probably point you to someone who can.
Happy ...

Pete,
Points well stated.
I looked at photos in Mindat of fluorite on sphalerite. Nearly all were cube- dodecahedral that could be discerned clearly.

Interesting indeed and quite a photo.
The small, attached crystal shows all the signs of being a twin. In particular the light growth shadow in the main crystal. It's slightly offset due to refractio ...

Perhaps this is Libyan Desert glass. But I don't think such is as hard as agate.

The picture I referenced is under Carles Millan's name.

The picture you feature under your name is cube-octahedral.

Last year at Tucson Carlos Meneses gave me a name for this, but I cannot find it now. Try getting in contact with him.

The purple shape appears to be hexoctahedral in nature, having three pairs of isosceles triangles centered around a triangular shape. You've definitely found the tri-fold axis of the cleaved octahedra ...

Pete,
Some of us call these 'Mayan Temple" habit fluorites. Yes, these are the result of smaller overgrowths on octahedral crystals. I have a specimen from Naica that has an octahedral phantom s ...

Nice piece and a good photo.
These are etched approximations of hexoctahedral faces on the cube, for which Jaimina stands out.

Another hint: In both cases there are four faces bordering cube faces. But they have differing orientation to the cube faces. Octahedral faces will develop off the corners of cube faces, dodecahedral ...

I'm sorry, I have to differ with Peter. These are cube and dodecahedral forms in combination.
It is a common problem to distinguish them from the cube-octahedral crystals.
On your two crystals the ...

Examine the outer edges where two crystals meet, like the edge to the upper right. Cyclic twins of rutile often have places where one crystal overlaps the other in ways that don't have similar develop ...

I too tried to figure how your rutile would be a single and couldn't find any way that worked. The dimpling indicates fairly strong dissolution. perhaps there was also some redeposition that filled i ...

On the prism faces I think I can see some 'mosaic' splitting, where imperfections in the crystal structure build up and there is slight splitting and subsequent growth of two parts slightly misaligned ...

Quartz with iron staining is common in Tamilnadu. Test for quartz.

This discussion is largely beyond my knowledge particularly of chemistry. The acicular growth of malachite within a euhedral azurite crystal seems to me to require dissolution of the azurite. Perhaps ...

Author	Message
Topic: Selective deposit on tourmaline
Bob Morgan Replies: 1 Views: 348	Forum: What is it? - Where is it from? Posted: Apr 04, 2024 16:21 Subject: Re: Selective deposit on tourmaline
Bob Morgan Replies: 1 Views: 348	There appears to be a third particularity - it's habit. I've looked through Goldschmidt and in other places and found no report of a large 001 face with adjoining 321 faces. In fact, there is no dis ...
Topic: Identification question
Bob Morgan Replies: 4 Views: 453	Forum: What is it? - Where is it from? Posted: Mar 29, 2024 20:12 Subject: Re: Identification question
Bob Morgan Replies: 4 Views: 453	There is a great mineral society in Baltimore with several members who have collected extensively locally. I'm sure they will be of help. It's the Baltimore, Maryland Chesapeake Bay Mineral Society ...
Topic: Can you recommend a lab to analyse specimens
Bob Morgan Replies: 29 Views: 10499	Forum: Minerals and Mineralogy Posted: Dec 31, 2023 22:33 Subject: Re: Can you recommend a lab to analyse specimens
Bob Morgan Replies: 29 Views: 10499	I found the names: Daniel Atencio at the University of Sao Paulo and Ricardo Scholz at the University of Duropraiso. If they can't do analyses, they can probably point you to someone who can. Happy ...
Topic: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Forum: Minerals and Mineralogy Posted: Dec 12, 2023 22:29 Subject: Re: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Pete, Points well stated. I looked at photos in Mindat of fluorite on sphalerite. Nearly all were cube- dodecahedral that could be discerned clearly.
Topic: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Forum: Minerals and Mineralogy Posted: Dec 12, 2023 18:03 Subject: Re: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Yes.
Topic: Nifontovite
Bob Morgan Replies: 8 Views: 3898	Forum: Minerals and Mineralogy Posted: Dec 09, 2023 12:38 Subject: Re: Nifontovite
Bob Morgan Replies: 8 Views: 3898	Interesting indeed and quite a photo. The small, attached crystal shows all the signs of being a twin. In particular the light growth shadow in the main crystal. It's slightly offset due to refractio ...
Topic: I want to know the sample
Bob Morgan Replies: 21 Views: 6676	Forum: What is it? - Where is it from? Posted: Dec 07, 2023 18:40 Subject: Re: I want to know the sample
Bob Morgan Replies: 21 Views: 6676	Perhaps this is Libyan Desert glass. But I don't think such is as hard as agate.
Topic: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Forum: Minerals and Mineralogy Posted: Dec 04, 2023 12:23 Subject: Re: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	The picture I referenced is under Carles Millan's name.
Topic: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Forum: Minerals and Mineralogy Posted: Dec 04, 2023 12:19 Subject: Re: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	The picture you feature under your name is cube-octahedral.
Topic: Can you recommend a lab to analyse specimens
Bob Morgan Replies: 29 Views: 10499	Forum: Minerals and Mineralogy Posted: Nov 29, 2023 21:15 Subject: Re: Can you recommend a lab to analyse specimens
Bob Morgan Replies: 29 Views: 10499	Last year at Tucson Carlos Meneses gave me a name for this, but I cannot find it now. Try getting in contact with him.
Topic: Fluorite Star
Bob Morgan Replies: 3 Views: 2966	Forum: Minerals and Mineralogy Posted: Nov 28, 2023 13:08 Subject: Re: Fluorite Star
Bob Morgan Replies: 3 Views: 2966	The purple shape appears to be hexoctahedral in nature, having three pairs of isosceles triangles centered around a triangular shape. You've definitely found the tri-fold axis of the cleaved octahedra ...
Topic: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Forum: Minerals and Mineralogy Posted: Nov 28, 2023 11:45 Subject: Re: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Pete, Some of us call these 'Mayan Temple" habit fluorites. Yes, these are the result of smaller overgrowths on octahedral crystals. I have a specimen from Naica that has an octahedral phantom s ...
Topic: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Forum: Minerals and Mineralogy Posted: Nov 27, 2023 11:59 Subject: Re: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Nice piece and a good photo. These are etched approximations of hexoctahedral faces on the cube, for which Jaimina stands out.
Topic: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Forum: Minerals and Mineralogy Posted: Nov 27, 2023 11:53 Subject: Re: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Another hint: In both cases there are four faces bordering cube faces. But they have differing orientation to the cube faces. Octahedral faces will develop off the corners of cube faces, dodecahedral ...
Topic: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	Forum: Minerals and Mineralogy Posted: Nov 27, 2023 11:50 Subject: Re: Fluorite crystallography?
Bob Morgan Replies: 27 Views: 9551	I'm sorry, I have to differ with Peter. These are cube and dodecahedral forms in combination. It is a common problem to distinguish them from the cube-octahedral crystals. On your two crystals the ...
Topic: About cyclic twinning - (5)
Bob Morgan Replies: 157 Views: 278266	Forum: Featured Columns of FMF Posted: Aug 29, 2023 16:40 Subject: Re: About cyclic twinning - (5)
Bob Morgan Replies: 157 Views: 278266	Examine the outer edges where two crystals meet, like the edge to the upper right. Cyclic twins of rutile often have places where one crystal overlaps the other in ways that don't have similar develop ...
Topic: About cyclic twinning - (5)
Bob Morgan Replies: 157 Views: 278266	Forum: Featured Columns of FMF Posted: Aug 28, 2023 06:38 Subject: Re: About cyclic twinning - (5)
Bob Morgan Replies: 157 Views: 278266	I too tried to figure how your rutile would be a single and couldn't find any way that worked. The dimpling indicates fairly strong dissolution. perhaps there was also some redeposition that filled i ...
Topic: Quartz: parallel growth or not?
Bob Morgan Replies: 3 Views: 6101	Forum: Minerals and Mineralogy Posted: Jul 21, 2023 08:08 Subject: Re: Quartz: parallel growth or not?
Bob Morgan Replies: 3 Views: 6101	On the prism faces I think I can see some 'mosaic' splitting, where imperfections in the crystal structure build up and there is slight splitting and subsequent growth of two parts slightly misaligned ...
Topic: Is this a diamond ?
Bob Morgan Replies: 2 Views: 7377	Forum: FOR BEGINNERS: What is it? Where is it from? Posted: Jul 17, 2023 13:54 Subject: Re: Is this a diamond ?
Bob Morgan Replies: 2 Views: 7377	Quartz with iron staining is common in Tamilnadu. Test for quartz.
Topic: Azurite to Malachite Chemistry
Bob Morgan Replies: 9 Views: 8461	Forum: Minerals and Mineralogy Posted: May 05, 2023 21:35 Subject: Re: Azurite to Malachite Chemistry
Bob Morgan Replies: 9 Views: 8461	This discussion is largely beyond my knowledge particularly of chemistry. The acicular growth of malachite within a euhedral azurite crystal seems to me to require dissolution of the azurite. Perhaps ...