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Newest topics and users posts
22 Sep-15:23:18 Re: collection of sante celiberti (Sante Celiberti)
22 Sep-12:56:04 Re: a mineralogical trip through the states of usa - indiana (R Saunders)
22 Sep-11:24:13 Re: a tri-state galena and calcite (Rgangue)
22 Sep-10:56:01 Re: a tri-state galena and calcite (R Saunders)
22 Sep-10:21:58 Re: northern ireland, ireland collecting sites (Rgangue)
22 Sep-10:18:31 Re: a tri-state galena and calcite (Rgangue)
22 Sep-09:43:12 Re: a tri-state galena and calcite (R Saunders)
22 Sep-09:12:01 Re: a mineralogical trip through the states of usa - indiana (R Saunders)
22 Sep-08:22:04 Re: collection of david carter (David916)
22 Sep-04:50:48 Re: very nice amethyst in the railroad works in north of spain (Heat)
22 Sep-04:11:45 Re: collection of volkmar stingl (Volkmar Stingl)
22 Sep-03:22:44 Re: very nice amethyst in the railroad works in north of spain (Hans Cremers)
22 Sep-03:11:53 Re: quartz and epidote with possible hedenbergite from imilchil, morocco (Sante Celiberti)
21 Sep-16:58:02 Quartz and epidote with possible hedenbergite from imilchil, morocco (Adam)
21 Sep-14:00:15 Re: very nice amethyst in the railroad works in north of spain (James Catmur)
21 Sep-13:57:11 Re: very nice amethyst in the railroad works in north of spain (James Catmur)
21 Sep-12:37:41 Re: very nice amethyst in the railroad works in north of spain (Heat)
21 Sep-09:15:23 Re: very nice amethyst in the railroad works in north of spain (Hans Cremers)
21 Sep-08:00:37 Re: very nice amethyst in the railroad works in north of spain (James Catmur)
21 Sep-07:40:10 Re: very nice amethyst in the railroad works in north of spain (Hans Cremers)
20 Sep-15:56:59 Re: collection of sante celiberti (Sante Celiberti)
20 Sep-14:58:07 Re: collection of sante celiberti (Bergur_e_sigurdarson)
20 Sep-14:21:07 Re: collection of sante celiberti (Sante Celiberti)
20 Sep-10:43:50 Re: very nice amethyst in the railroad works in north of spain (James Catmur)
20 Sep-09:18:06 Re: collection of carles millan (Carles Millan)

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  Topic: Sold as “Green stilbite”
Pete Richards

Replies: 11
Views: 738

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Sep 16, 2021 15:44   Subject: Re: Sold as “Green stilbite”
It bears emphasis that garnet is the name of a mineral, while greenschist is the name of a metamorphic rock. I don't claim to be a petrologist, but I believe "greenschist" implies a certain ...
  Topic: Mookaite?
Pete Richards

Replies: 2
Views: 347

PostForum: What is it? - Where is it from?   Posted: Aug 28, 2021 15:02   Subject: Re: Mookaite?
Mookaite is not an official mineral name. It is better described as the name of a rock composed mostly of silica from the skeletons of radiolaria, and is properly applied to rock from a particular lo ...
  Topic: About cyclic twinning - (5)
Pete Richards

Replies: 144
Views: 203349

PostForum: Featured Columns of FMF   Posted: Aug 06, 2021 10:19   Subject: Re: About cyclic twinning - (5)
Several isometric minerals form fivelings, including diamond, copper, gold, and I think silver.
  Topic: Black, metallic, yellow oxide?
Pete Richards

Replies: 23
Views: 1896

PostForum: What is it? - Where is it from?   Posted: Jul 21, 2021 20:28   Subject: Re: Black, metallic, yellow oxide?
the first one suggests brookite (orthorhombic) altering to earthy anatase. The second one does not....

I don't know how this fits with the apparent cleavages.
  Topic: Linarite or azurite
Pete Richards

Replies: 5
Views: 1124

PostForum: Conserving, Preparing and Cleaning Minerals   Posted: Jul 12, 2021 14:52   Subject: Re: Linarite or azurite
I have a note in my catalog describing subjecting linarite to dilute HCl. It did not fizz but dissolved slowly, producing a white coating on the linarite. This was a specimen from the Dunbrack Mine ...
  Topic: Help with historical stone mystery - slag, or something else?
Pete Richards

Replies: 11
Views: 1241

PostForum: What is it? - Where is it from?   Posted: Jun 25, 2021 12:51   Subject: Re: Help with historical stone mystery - slag, or something else?
note the exact date they were found and see if anywhere upwind
A good idea. But I think (any true petrologists, please confirm) that really light (floatable) pumice is probably rhyolitic in nature, ...
  Topic: Help with historical stone mystery - slag, or something else?
Pete Richards

Replies: 11
Views: 1241

PostForum: What is it? - Where is it from?   Posted: Jun 25, 2021 10:38   Subject: Re: Help with historical stone mystery - slag, or something else?
This is an interesting question. I suppose the overlap in chemical composition could be considerable between the two sources, depending on the nature of the iron ore. I think the analyses use archai ...
  Topic: Unknown mineral from Pikes Peak pegmatite
Pete Richards

Replies: 23
Views: 2827

PostForum: What is it? - Where is it from?   Posted: Jun 13, 2021 21:06   Subject: Re: Unknown mineral from Pikes Peak pegmatite
Phenakite?
Good thought. Right environment, right general color or lack thereof.

However, phenakite is trigonal and typically occurs as prismatic crystals with a hexagonal outline. The crystal s ...
  Topic: Unknown mineral from Pikes Peak pegmatite
Pete Richards

Replies: 23
Views: 2827

PostForum: What is it? - Where is it from?   Posted: Jun 13, 2021 20:55   Subject: Re: Unknown mineral from Pikes Peak pegmatite
Re: "Harder than steel"
That is true of euclase and danburite... and topaz and a number of other minerals.
  Topic: Unknown mineral from Pikes Peak pegmatite
Pete Richards

Replies: 23
Views: 2827

PostForum: What is it? - Where is it from?   Posted: Jun 13, 2021 16:50   Subject: Re: Unknown mineral from Pikes Peak pegmatite
Your point about the cleavage is also a good one, Peter. I plead guilty to responding without research. The perfect cleavage of euclase is {010}, which would be perpendicular to the second view, if ...
  Topic: Unknown mineral from Pikes Peak pegmatite
Pete Richards

Replies: 23
Views: 2827

PostForum: What is it? - Where is it from?   Posted: Jun 13, 2021 16:27   Subject: Re: Unknown mineral from Pikes Peak pegmatite
What about euclase? I have no idea what the local mineral assemblage is, so this is in that sense a shot in the dark.

The top view of the crystal suggests that it is really monoclinic, not orthorh ...
  Topic: A new mineral: alpha-calcium formate
Pete Richards

Replies: 9
Views: 2107

PostForum: Minerals and Mineralogy   Posted: May 02, 2021 20:45   Subject: Re: A new mineral: alpha-calcium formate
The old notion that minerals must be free of anthropogenic or other biologic influence , and must be inorganic chemical compounds, has long become one of mostly historic interest, with some organic sa ...
  Topic: Calcite form
Pete Richards

Replies: 6
Views: 1396

PostForum: Minerals and Mineralogy   Posted: Apr 25, 2021 16:34   Subject: Re: Calcite form
(snip)...
Anybody knows how many calcite forms are listed in Goldschmidt Atlas der Krystallformen?
...

It is necessary to distinguish between the term "form" in the strict crystallo ...
  Topic: Calcite form
Pete Richards

Replies: 6
Views: 1396

PostForum: Minerals and Mineralogy   Posted: Apr 25, 2021 12:00   Subject: Re: Calcite form
I think those forms are pretty reasonable guesses. {012} for sure. {0 16 1} is possible. {541} is about in the right place.

Attached is a smorf drawing I made of a crystal with these forms. Anyon ...
  Topic: Hillman Hall of Minerals and Gems
Pete Richards

Replies: 9
Views: 1684

PostForum: Other Museums in USA   Posted: Apr 11, 2021 08:14   Subject: Re: Hillman Hall of Minerals and Gems
It is an excellent mineral museum. Enjoy it. But check before you go to make sure they are open!
  Topic: Melanophlogite?
Pete Richards

Replies: 11
Views: 2744

PostForum: What is it? - Where is it from?   Posted: Apr 07, 2021 13:27   Subject: Re: Melanophlogite?
From the photograph, I would have to guess quartz, maybe including broken fragments of a fine-grained quartz like jasper. Of the options you list, none is reasonable except chalcedony, both because t ...
  Topic: what stones are these?
Pete Richards

Replies: 15
Views: 2725

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Mar 23, 2021 13:09   Subject: Re: what stones are these?
I agree that it's not granite, and it's due to the lack of color, or at least the lack of color variety. Granite has quartz, which is usually transucent grey, feldspar which can be white or pink, and ...
  Topic: Found in Peoria Arizona, please help identify. Not my normal find.
Pete Richards

Replies: 7
Views: 1539

PostForum: FOR BEGINNERS: What is it? Where is it from?   Posted: Mar 22, 2021 20:39   Subject: Re: Found in Peoria Arizona, please help identify. Not my normal find.
Nice photograph! Is the object about 1/4"?

In order to help you further we need some information that you can provide. Will one of these objects fizz in warm vinegar? Will an edge of one scr ...
  Topic: In-situ photos at Pizzo Forno, Alpe Sponda (Ticino) ?
Pete Richards

Replies: 7
Views: 2157

PostForum: Mines and Mineral Localities   Posted: Mar 18, 2021 12:38   Subject: Re: In-situ photos at Pizzo Forno, Alpe Sponda (Ticino) ?
I heard once from a credible source that Pizzo Forno is a dummy locality, selected by the Strahlers to prevent people from learning of the real location of the wonderful kyanite and staurolite specime ...
  Topic: Creedite - Is Pink Different than Purple, Navidad Mine (Mina Navidad)
Pete Richards

Replies: 9
Views: 2544

PostForum: Minerals and Mineralogy   Posted: Mar 08, 2021 19:19   Subject: Re: Creedite - Is Pink Different than Purple, Navidad Mine (Mina Navidad)
Looks to me like it may be a question of the color of the matrix underneath the crystals. Purple creedite is on dark-colored matrix, pink is on light colored matrix or is thick enough that the matrix ...
 
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