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23 Jun-02:55:37 Re: the mizunaka collection - quartz (Am Mizunaka)
22 Jun-23:18:14 Re: favourite quartzes? (Eck Noch)
22 Jun-16:03:24 Re: a mineralogical trip through italy by sante celiberti (Sante Celiberti)
22 Jun-09:54:22 Re: the mizunaka collection - quartz (Eck Noch)
22 Jun-06:10:26 Re: un-registering from this website (Jordi Fabre)
22 Jun-05:58:21 Un-registering from this website (Peter@vanpeborgh.Eu)
22 Jun-02:58:37 Re: the mizunaka collection - quartz (Tobi)
22 Jun-02:52:08 Re: favourite barytes? (Tobi)
21 Jun-14:26:22 Re: a mineralogical trip through italy by sante celiberti (Sante Celiberti)
20 Jun-15:26:42 Re: a mineralogical trip through italy by sante celiberti (Sante Celiberti)
20 Jun-15:18:37 Re: favourite barytes? (Bob Harman)
20 Jun-14:06:36 Re: virtual shows: what's the concept? (Cascaillou)
19 Jun-15:10:35 Re: a mineralogical trip through italy by sante celiberti (Sante Celiberti)
19 Jun-12:45:26 Re: collection of volkmar stingl (Volkmar Stingl)
18 Jun-13:54:07 Re: virtual shows: what's the concept? (Bob Harman)
18 Jun-12:05:04 Re: virtual shows: what's the concept? (James Catmur)
18 Jun-10:14:30 Re: where can i find some bio on gilbert gauthier? (Roger Warin)
18 Jun-08:55:35 Virtual shows: what's the concept? (Cascaillou)
18 Jun-06:55:44 Re: mineral spirituality? (Cascaillou)
17 Jun-22:41:26 Re: collection of volkmar stingl (Volkmar Stingl)
17 Jun-22:09:17 Re: don lum collection (Volkmar Stingl)
17 Jun-17:03:23 Re: don lum collection (Don Lum)
17 Jun-16:11:13 Re: the mizunaka collection - quartz (Am Mizunaka)
17 Jun-15:57:24 Re: where can i find some bio on gilbert gauthier? (Pub1tzu)
17 Jun-15:44:54 Re: a mineralogical trip through italy by sante celiberti (Sante Celiberti)

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  Topic: Is this still quartz??
Amir Akhavan

Replies: 7
Views: 897

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: May 14, 2021 13:16   Subject: Re: Is this still quartz??
Most likely chalcedony, as Alfredo said.

The looks can be deceiving ;-)
The rock in the attached photo is > 95% quartz.
  Topic: How does color treating "work"?
Amir Akhavan

Replies: 6
Views: 755

PostForum: Off-Topic and Introductions   Posted: Apr 24, 2021 07:14   Subject: Re: How does color treating "work"?
>> and neither should change the chemical composition of the mineral.

Oh yes, it does.
It does not change the bulk composition of the material, that is, when you powderize and analyze the am ...
  Topic: Synthetic smoky quartz?
Amir Akhavan

Replies: 11
Views: 1141

PostForum: Minerals and Mineralogy   Posted: Apr 12, 2021 11:08   Subject: Re: Synthetic smoky quartz?
Yes, synthetic.

Needles are typical and a common byproduct in industrial crystal growth, and form on the walls of the vessels, even though the seeds and the oscillator crystals grown from them are ...
  Topic: Quartz Points locality
Amir Akhavan

Replies: 10
Views: 1441

PostForum: What is it? - Where is it from?   Posted: Mar 08, 2021 10:29   Subject: Re: Quartz Points locality
Where did you buy it?

It looks a bit like an alpine-type fissure specimen, because the cavity has opened perpendicular to the bedding of the host rock.

It reminds me of specimens from Vizille an ...
  Topic: Betafo habit?
Amir Akhavan

Replies: 5
Views: 1651

PostForum: Minerals and Mineralogy   Posted: Feb 20, 2021 17:03   Subject: Re: Betafo habit?
Just in case someone is missing it: the "all wrong" quartz is right-handed :-)
  Topic: Betafo habit?
Amir Akhavan

Replies: 5
Views: 1651

PostForum: Minerals and Mineralogy   Posted: Feb 19, 2021 19:56   Subject: Re: Betafo habit?
Sorry for the misunderstanding, I wasn't thinking of "common x s combos" at Corinto/Curvelo, but common elongated s faces on Dauphiné habit crystals from there. "Common" is relativ ...
  Topic: Petrified wood?
Amir Akhavan

Replies: 12
Views: 2227

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Feb 19, 2021 14:48   Subject: Re: Petrified wood?
The fibers apparently belong to the green, partially altered and brown material - this was the material I suggested to test for hardness.
The blue crystals (that look black or dark gray on my comput ...
  Topic: Petrified wood?
Amir Akhavan

Replies: 12
Views: 2227

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Feb 19, 2021 14:32   Subject: Re: Petrified wood?
If the mineral is rather soft (easily scratched by glass), it's a probably a serpentine-group mineral, and asbestos - no worries, it won't bite, just use common sense when handling and don't, for exam ...
  Topic: Petrified wood?
Amir Akhavan

Replies: 12
Views: 2227

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Feb 19, 2021 14:19   Subject: Re: Petrified wood?
Does it have a splintery fracture or do fibers come off?
My first impression of the specimen is simply serpentine asbestos (antigorite or the like), I don't think this is petrified wood.
  Topic: Betafo habit?
Amir Akhavan

Replies: 5
Views: 1651

PostForum: Minerals and Mineralogy   Posted: Feb 19, 2021 14:09   Subject: Re: Betafo habit?
There are no "official terms" when it comes to habits, just names for general appearences of crystals that people use or don't use, it's fairly wishy-washy, but there are some "well-est ...
  Topic: Mysterious Red Pyramids in Mexican opal
Amir Akhavan

Replies: 8
Views: 1977

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Jan 23, 2021 15:33   Subject: Re: Mysterious Red Pyramids in Mexican opal
I agree with Bob that this could be artificial, some hard epoxy or the like.
You should get it tested.
Specific weight would help.
  Topic: Natural heat treating
Amir Akhavan

Replies: 8
Views: 2314

PostForum: Off-Topic and Introductions   Posted: Dec 27, 2020 18:19   Subject: Re: Natural heat treating
Interesting observation, Mark. 300-400°C would be enough and pale the crystals within a few hours, higher temperatures would work much quicker.
  Topic: Pink amethyst?
Amir Akhavan

Replies: 7
Views: 5780

PostForum: Mineralogical Literature   Posted: Oct 10, 2020 10:01   Subject: Re: Pink amethyst?
There's actually no problem with people giving the specimens they find in "their valley" all sorts of names.
The trouble starts when all these "local names" are used for similarly ...
  Topic: Very steep rhombohedral calcite?
Amir Akhavan

Replies: 14
Views: 4207

PostForum: Minerals and Mineralogy   Posted: Oct 06, 2020 18:34   Subject: Re: Very steep rhombohedral calcite?
The high indices as shown in the crystal drawing program are also a result of using the old a:c ratio of 1:0.854.
The new value that actually reflects the crystal structure according to new measurem ...
  Topic: Opaque black Quartz, Locality info/matrix info?
Amir Akhavan

Replies: 21
Views: 6118

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Jul 14, 2020 03:21   Subject: Re: Opaque black Quartz, Locality info/matrix info?
It looks like a specimen from a pegmatite, smoky quartz + microcline, covered by chabazite (typical slightly skewed "cubes") and its common associate stilbite.
Nevertheless, doing a "f ...
  Topic: Pink amethyst?
Amir Akhavan

Replies: 7
Views: 5780

PostForum: Mineralogical Literature   Posted: May 06, 2020 19:23   Subject: Re: Pink amethyst?
I'm not really fond of marketing-driven names like "pink amethyst" and wouldn't advocate using such a term.
But they could have done worse: they could have called it "pink quartz" ...
  Topic: What type of quartz is this?
Amir Akhavan

Replies: 11
Views: 8305

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Mar 15, 2020 04:46   Subject: Re: What type of quartz is this?
This is probably chert (made mostly of chalcedony).
The piece under it with the white "crust" is definitely chert. If they both came from the same spot you got your answer.
Looks a bit li ...
  Topic: Smoky Quartz or Smoky Glass?
Amir Akhavan

Replies: 21
Views: 8242

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Jan 12, 2020 13:44   Subject: Re: Smoky Quartz or Smoky Glass?
smoky quartz dichroism example
https://www.mindat.org/min-3689.html
  Topic: Smoky Quartz or Smoky Glass?
Amir Akhavan

Replies: 21
Views: 8242

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Jan 11, 2020 20:42   Subject: Re: Smoky Quartz or Smoky Glass?
> Should the monitor screen be white as in a blank page in a browser when I try this?

yes
It won't work with one of these cathode ray tube monitors, of course, but everything else should work, ...
  Topic: Smoky Quartz or Smoky Glass?
Amir Akhavan

Replies: 21
Views: 8242

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Jan 11, 2020 10:00   Subject: Re: Smoky Quartz or Smoky Glass?
The easiest non-destructive way to test *colored* quartz varieties is dichroism.
Just rotate the specimen in front of a computer monitor or a polarizer filter and check for changes in color or hue.
...
 
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