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Search found 217 matches |
Author | Message |
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Topic: Selective deposit on tourmaline | |
Bob Morgan Replies: 1 Views: 553 |
Forum: What is it? - Where is it from? Posted: Apr 04, 2024 16:21 Subject: Re: Selective deposit on tourmaline |
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 ... |
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Topic: Identification question | |
Bob Morgan Replies: 4 Views: 667 |
Forum: What is it? - Where is it from? Posted: Mar 29, 2024 20:12 Subject: Re: Identification question |
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 ... |
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Topic: Can you recommend a lab to analyse specimens | |
Bob Morgan Replies: 29 Views: 11226 |
Forum: Minerals and Mineralogy Posted: Dec 31, 2023 22:33 Subject: Re: Can you recommend a lab to analyse specimens |
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 ... |
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Topic: Fluorite crystallography? | |
Bob Morgan Replies: 27 Views: 10123 |
Forum: Minerals and Mineralogy Posted: Dec 12, 2023 22:29 Subject: Re: Fluorite crystallography? |
Pete,
Points well stated. I looked at photos in Mindat of fluorite on sphalerite. Nearly all were cube- dodecahedral that could be discerned clearly. |
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Topic: Fluorite crystallography? | |
Bob Morgan Replies: 27 Views: 10123 |
Forum: Minerals and Mineralogy Posted: Dec 12, 2023 18:03 Subject: Re: Fluorite crystallography? |
Yes. | |
Topic: Nifontovite | |
Bob Morgan Replies: 8 Views: 4357 |
Forum: Minerals and Mineralogy Posted: Dec 09, 2023 12:38 Subject: Re: Nifontovite |
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 ... |
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Topic: I want to know the sample | |
Bob Morgan Replies: 21 Views: 6799 |
Forum: What is it? - Where is it from? Posted: Dec 07, 2023 18:40 Subject: Re: I want to know the sample |
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: 10123 |
Forum: Minerals and Mineralogy Posted: Dec 04, 2023 12:23 Subject: Re: Fluorite crystallography? |
The picture I referenced is under Carles Millan's name. | |
Topic: Fluorite crystallography? | |
Bob Morgan Replies: 27 Views: 10123 |
Forum: Minerals and Mineralogy Posted: Dec 04, 2023 12:19 Subject: Re: Fluorite crystallography? |
The picture you feature under your name is cube-octahedral. | |
Topic: Can you recommend a lab to analyse specimens | |
Bob Morgan Replies: 29 Views: 11226 |
Forum: Minerals and Mineralogy Posted: Nov 29, 2023 21:15 Subject: Re: Can you recommend a lab to analyse specimens |
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: 3195 |
Forum: Minerals and Mineralogy Posted: Nov 28, 2023 13:08 Subject: Re: Fluorite Star |
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: 10123 |
Forum: Minerals and Mineralogy Posted: Nov 28, 2023 11:45 Subject: Re: Fluorite crystallography? |
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 ... |
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Topic: Fluorite crystallography? | |
Bob Morgan Replies: 27 Views: 10123 |
Forum: Minerals and Mineralogy Posted: Nov 27, 2023 11:59 Subject: Re: Fluorite crystallography? |
Nice piece and a good photo.
These are etched approximations of hexoctahedral faces on the cube, for which Jaimina stands out. |
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Topic: Fluorite crystallography? | |
Bob Morgan Replies: 27 Views: 10123 |
Forum: Minerals and Mineralogy Posted: Nov 27, 2023 11:53 Subject: Re: Fluorite crystallography? |
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: 10123 |
Forum: Minerals and Mineralogy Posted: Nov 27, 2023 11:50 Subject: Re: Fluorite crystallography? |
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 ... |
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Topic: About cyclic twinning - (5) | |
Bob Morgan Replies: 157 Views: 279114 |
Forum: Featured Columns of FMF Posted: Aug 29, 2023 16:40 Subject: Re: About cyclic twinning - (5) |
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: 279114 |
Forum: Featured Columns of FMF Posted: Aug 28, 2023 06:38 Subject: Re: About cyclic twinning - (5) |
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: 6329 |
Forum: Minerals and Mineralogy Posted: Jul 21, 2023 08:08 Subject: Re: Quartz: parallel growth or not? |
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: 7435 |
Forum: FOR BEGINNERS: What is it? Where is it from? Posted: Jul 17, 2023 13:54 Subject: Re: Is this a diamond ? |
Quartz with iron staining is common in Tamilnadu. Test for quartz. | |
Topic: Azurite to Malachite Chemistry | |
Bob Morgan Replies: 9 Views: 8747 |
Forum: Minerals and Mineralogy Posted: May 05, 2023 21:35 Subject: Re: Azurite to Malachite Chemistry |
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 ... | |
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