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28 Jan-17:04:56 Re: tucson shows 2022 (Bob Kerr)
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28 Jan-14:41:04 Re: don lum collection (Carles Millan)
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28 Jan-13:46:21 Re: don lum collection (Don Lum)
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28 Jan-00:09:13 Re: don lum collection (Don Lum)
27 Jan-18:53:28 Re: collection of sante celiberti (Sante Celiberti)
27 Jan-18:07:20 Re: tucson shows 2022 (Bob Kerr)
27 Jan-17:13:53 Re: tucson shows 2022 (Bob Kerr)
27 Jan-16:47:57 Re: tucson shows 2022 (Bob Kerr)
27 Jan-16:33:00 Re: tucson shows 2022 (Bob Kerr)
27 Jan-16:22:17 Re: tucson shows 2022 (Bob Kerr)
27 Jan-16:04:48 Re: tucson shows 2022 (Bob Kerr)
27 Jan-15:04:20 Re: forms involved in titanite crystal (Josele)
27 Jan-14:20:21 Re: alleged 'silvers' from udokan? (Jordi Fabre)
27 Jan-14:17:25 Re: collection of michael shaw (Michael Shaw)
27 Jan-10:56:11 Re: tucson shows 2022 (Joseph Doliveira)
27 Jan-10:52:00 Re: tucson shows 2022 (John S. White)
27 Jan-10:06:30 Re: tucson shows 2022 (Minsur)
27 Jan-10:00:18 Re: forms involved in titanite crystal (Mark Holtkamp)
26 Jan-20:54:37 Re: tucson shows 2022 (Bob Kerr)

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  Topic: Forms Involved in Titanite Crystal
Josele

Replies: 18
Views: 928

PostForum: Minerals and Mineralogy   Posted: Jan 27, 2022 15:04   Subject: Re: Forms Involved in Titanite Crystal
Understood, thank you Mark.
Better we forget last image, these "polaroid" old glasses do very weird things when you turn one of them over facing the polarized computer light.
  Topic: Forms Involved in Titanite Crystal
Josele

Replies: 18
Views: 928

PostForum: Minerals and Mineralogy   Posted: Jan 26, 2022 09:03   Subject: Re: Forms Involved in Titanite Crystal
... the direction of extinction angles between crossed polarizers would be helpful.
I have not a petrographic microscope with nicols but I found two old "Polaroid" plastic glasses that can ...
  Topic: Forms Involved in Titanite Crystal
Josele

Replies: 18
Views: 928

PostForum: Minerals and Mineralogy   Posted: Jan 23, 2022 11:08   Subject: Re: Forms Involved in Titanite Crystal
... What colors do you see if you turn the crystal 90 degrees along the long axis? But maybe the crystal is too thick in this direction to get a good view of the colors.
Yes, too thick, in c-axis di ...
  Topic: Forms Involved in Titanite Crystal
Josele

Replies: 18
Views: 928

PostForum: Minerals and Mineralogy   Posted: Jan 23, 2022 08:18   Subject: Re: Forms Involved in Titanite Crystal
Well, I think we got it!

Mark, I have not Nicols to check extinction angles, but it is quite pleochroic. Following your advice everything falls into place.

Pete, your first scheme fits perfectly ...
  Topic: Forms Involved in Titanite Crystal
Josele

Replies: 18
Views: 928

PostForum: Minerals and Mineralogy   Posted: Jan 21, 2022 21:35   Subject: Re: Forms Involved in Titanite Crystal
Bob, thanks for the push, I had not done any test until today.
I just checked hardness, it scratches fluorite easily and do not scratch pyrite, so it’s into titanite range.
I released the crystal fr ...
  Topic: Forms Involved in Titanite Crystal
Josele

Replies: 18
Views: 928

PostForum: Minerals and Mineralogy   Posted: Jan 21, 2022 15:47   Subject: Re: Forms Involved in Titanite Crystal
Geometrical crystallography is fascinating, what I enjoy most about minerals. When I get an atypical crystal, the process to know what polyhedrons, forms or planes are involved, spinning round and rou ...
  Topic: Forms Involved in Titanite Crystal
Josele

Replies: 18
Views: 928

PostForum: Minerals and Mineralogy   Posted: Jan 20, 2022 14:53   Subject: Re: Forms Involved in Titanite Crystal
Do not apologize, that was a great help. I was not aware of these differences in titanite cell.

Then I must return to the start line. It took me quite long time elaborating my misleaded speculation ...
  Topic: Forms Involved in Titanite Crystal
Josele

Replies: 18
Views: 928

PostForum: Minerals and Mineralogy   Posted: Jan 20, 2022 10:52   Subject: Forms Involved in Titanite Crystal
I'm trying to understand this titanite crystal but I have more doubts than certainties. Maybe you can help? Thanks in advance.
  Topic: Seeking methodology for identifying crystalline forms.
Josele

Replies: 11
Views: 834

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Jan 04, 2022 13:23   Subject: Re: Seeking methodology for identifying crystalline forms.
Bob, right, four 3-fold axis defines the isometric system! it can have three or none 4-fold symmetry axis according to its class.

This is the link to Don Peck article recommended by Pete: The isome ...
  Topic: Epitaxial rutile
Josele

Replies: 18
Views: 26646

PostForum: Minerals and Mineralogy   Posted: Nov 25, 2021 10:27   Subject: Epitaxial or twinned rutile?
I have not photomicrography equipment but recently I bough a mobile phone with microscope camera (30x). Depth of field is very short, focal length is fixed and there is no possibility of stacking phot ...
  Topic: Kamar Safed emerald mine in Panjshir, Afghanistan
Josele

Replies: 4
Views: 1716

PostForum: Mines and Mineral Localities   Posted: Sep 25, 2021 15:05   Subject: Re: Kamar Safed emerald mine in Panjshir, Afghanistan
Gérard, thanks for the link and extra info.
Kamar Safed Mindat page at first placed the mine in Bazarak District, later was changed to Paryan District and finally edited by me to Khenj District.
Aft ...
  Topic: Kamar Safed emerald mine in Panjshir, Afghanistan
Josele

Replies: 4
Views: 1716

PostForum: Mines and Mineral Localities   Posted: Sep 25, 2021 05:41   Subject: Re: Kamar Safed emerald mine in Panjshir, Afghanistan
I see you have created a new locality in FMF database but to my understanding Kamad Safed should be in the lower level of hierarchy: Kamar Safed mine, Khenj emerald area, Khenj District, Panjshir Prov ...
  Topic: Kamar Safed emerald mine in Panjshir, Afghanistan
Josele

Replies: 4
Views: 1716

PostForum: Mines and Mineral Localities   Posted: Sep 25, 2021 05:08   Subject: Kamar Safed emerald mine in Panjshir, Afghanistan
After reading Gerard's comment about the Panjshir emerald deposit and the locality given to an emerald specimen, Kamar Safed ( https://www.mineral-forum.com/message-board/viewtopic.php?p=76414#76414 ) ...
  Topic: Fulgurite
Josele

Replies: 8
Views: 1834

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Sep 15, 2021 09:56   Subject: Re: Fulgurite
In this blurry photo it looks like a rhyolite pebble more than fulgurite. Well focused close-up images can help a lot but maybe a petrographic study is needed to be sure.
  Topic: Mineral questions from a woodworker!
Josele

Replies: 3
Views: 1379

PostForum: Off-Topic and Introductions   Posted: Sep 06, 2021 10:35   Subject: Re: Mineral questions from a woodworker!
A quick look on the Internet gives some interesting results:
- Making pigments or paint from minerals
- Mineral Pigments in Archaeology: Their Analysis and the Range of Available Materials
- How Na ...
  Topic: Probable ruby/garnet mix?
Josele

Replies: 7
Views: 1380

PostForum: What is it? - Where is it from?   Posted: Aug 27, 2021 05:53   Subject: Re: Probable ruby/garnet mix?
Fluorescence color alone is not a definitive way to recognize mineral species. White stuff fluorescing red could be also calcite.
In other hand, feldspar with red fluorescence use to be plagioclase m ...
  Topic: Calcite form
Josele

Replies: 6
Views: 2037

PostForum: Minerals and Mineralogy   Posted: Apr 26, 2021 11:17   Subject: Re: Calcite form
Thanks for these impressive calcite data. I suppose calcite is the specie with the largest number of documented combinations of basic forms. Is that true? More than fluorite?

This is another remark ...
  Topic: Calcite form
Josele

Replies: 6
Views: 2037

PostForum: Minerals and Mineralogy   Posted: Apr 25, 2021 15:53   Subject: Re: Calcite form
Thanks for your comments.

A calcite dedicated page that for sure you know well was a great help for determining most common steep scalenohedron forms: http://nsminerals.atspace.com/calcite.html

...
  Topic: Calcite form
Josele

Replies: 6
Views: 2037

PostForum: Minerals and Mineralogy   Posted: Apr 25, 2021 10:19   Subject: Calcite form
I've been trying to determine Miller indices of a calcite specimen from Iraí, Brazil. I think it could be a combination of very steep rhombohedron, something like {0.16.1}, finished by the flat rhombo ...
  Topic: Synthetic smoky quartz?
Josele

Replies: 11
Views: 2784

PostForum: Minerals and Mineralogy   Posted: Apr 11, 2021 16:14   Subject: Re: Synthetic smoky quartz?
I think it is a lab grown quartz.

There are many offers of this stuff in ebay, Sellers says it is natural but...
 
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