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This is a very interesting, obviously twisted crystal. I have never seen one like it. Perhaps you should have purchased all 30 of them!

My own opinion (since Roger asked) is that this should not ...

Where is the skutterudite? What is the purple mineral? This looks rather different from typical material from Cobalt, Ontario. What do the Canadians among us think?

I don't know about the locality, but I have some doubts whether these are really pericline twins. They look more like normal (but nicely formed) albite twins to me.

Thanks for posting some very interesting crystals!

Bob Morgan made some good comments, with which I agree. I will add some additional thoughts, hopefully helpful.

I want to try to make a genera ...

This is an amazing change!

Does any part of the dendrite intersect the surface of the cabochon, including the "stem"?

Frondel, in Dana's System of Mineralogy 7th edition vol. 3 pag3 81 figures 4 and 5 illustrates Dauphiné contact twins. In these, there are two crystals in contact along their lengths, with their c-a ...

An interesting post, Roger, and two very nice specimens. Yes, Dauphiné twins. Probably.

As it happens, Carl Francis and I have just published an article in Rocks & Minerals on Brazil-law twin ...

These crystals are rhombohedra.

If it's non-magnetic, it is not an iron meteorite.

Consider the possibility that it is a partially-refined metal - a smelting product - rather than a natural rock or mineral.

My guess is that it is quartz, based on the appearance of the columns in close-up. It could also be barite or gypsum, which are known to form similar stretch textures.

A magnet will tell you if magnetite is present, but I don't see anything that looks like magnetite. As helvine or genthelvite it is much more valuable than garnet!

Here is a suggestive citation from the Axinite page of Mindat:

Gautron, Laurent, Meisser, Nicolas (2001) Prehnite from La Combe De La Selle, Saint Christophe-en-Oisans, Isère, France. The Mineralog ...

Germany (or Austria) certainly seems to make the most sense. As for Switzerland, a Mindat search for "Grube" (mine or pit) with no further locality specification brings up only two matches i ...

It appears that the orange color was deposited by growth on the (0001) end faces of the crystal, and perhaps was not deposited at all in the earliest period of growth. The question then becomes, what ...

I am sorry, but I think it is very unlikely that the purple prism is amethyst. Perhaps there is a thin film of quartz on the purple mineral that gave a deceptive reading.

Author	Message
Topic: Gwindel Skutterudite?
Pete Richards Replies: 3 Views: 456	Forum: Minerals and Mineralogy Posted: Jun 29, 2025 13:59 Subject: Re: Gwindel Skutterudite?
Pete Richards Replies: 3 Views: 456	This is a very interesting, obviously twisted crystal. I have never seen one like it. Perhaps you should have purchased all 30 of them! My own opinion (since Roger asked) is that this should not ...
Topic: Skutterudite
Pete Richards Replies: 4 Views: 877	Forum: Micros & Macros - Images of Minerals Posted: Jun 04, 2025 20:01 Subject: Re: Skutterudite
Pete Richards Replies: 4 Views: 877	Where is the skutterudite? What is the purple mineral? This looks rather different from typical material from Cobalt, Ontario. What do the Canadians among us think?
Topic: Locality for Albite from the Dauphiné
Pete Richards Replies: 3 Views: 956	Forum: FOR BEGINNERS: What is it? Where is it from? Posted: May 26, 2025 15:13 Subject: Re: Locality for albite from Dauphine
Pete Richards Replies: 3 Views: 956	I don't know about the locality, but I have some doubts whether these are really pericline twins. They look more like normal (but nicely formed) albite twins to me.
Topic: Quartz Twins
Pete Richards Replies: 6 Views: 2430	Forum: Minerals and Mineralogy Posted: May 07, 2025 08:22 Subject: Re: Quartz Twins
Pete Richards Replies: 6 Views: 2430	Thanks for posting some very interesting crystals! Bob Morgan made some good comments, with which I agree. I will add some additional thoughts, hopefully helpful. I want to try to make a genera ...
Topic: Ghost dendrite
Pete Richards Replies: 7 Views: 2116	Forum: Minerals and Mineralogy Posted: May 02, 2025 18:34 Subject: Re: Ghost dendrite
Pete Richards Replies: 7 Views: 2116	This is an amazing change! Does any part of the dendrite intersect the surface of the cabochon, including the "stem"?
Topic: A true morphological twin of quartz according to the Dauphiné law.
Pete Richards Replies: 5 Views: 3292	Forum: What is it? - Where is it from? Posted: Mar 03, 2025 18:01 Subject: Re: A true morphological twin of quartz according to the Dauphiné law.
Pete Richards Replies: 5 Views: 3292	Frondel, in Dana's System of Mineralogy 7th edition vol. 3 pag3 81 figures 4 and 5 illustrates Dauphiné contact twins. In these, there are two crystals in contact along their lengths, with their c-a ...
Topic: A true morphological twin of quartz according to the Dauphiné law.
Pete Richards Replies: 5 Views: 3292	Forum: What is it? - Where is it from? Posted: Mar 02, 2025 20:20 Subject: Re: A true morphological twin of quartz according to the Dauphiné law.
Pete Richards Replies: 5 Views: 3292	An interesting post, Roger, and two very nice specimens. Yes, Dauphiné twins. Probably. As it happens, Carl Francis and I have just published an article in Rocks & Minerals on Brazil-law twin ...
Topic: Calcite crystal habit
Pete Richards Replies: 3 Views: 2190	Forum: FOR BEGINNERS: What is it? Where is it from? Posted: Feb 23, 2025 16:09 Subject: Re: Calcite crystal habit
Pete Richards Replies: 3 Views: 2190	These crystals are rhombohedra.
Topic: I’ve exhausted all local help! Please help me identify this?
Pete Richards Replies: 4 Views: 2946	Forum: What is it? - Where is it from? Posted: Feb 06, 2025 13:32 Subject: Re: I’ve exhausted all local help! Please help me identify this?
Pete Richards Replies: 4 Views: 2946	If it's non-magnetic, it is not an iron meteorite. Consider the possibility that it is a partially-refined metal - a smelting product - rather than a natural rock or mineral.
Topic: Unknown banded mineral from shores of lake Buttermere, Cumbria. UK
Pete Richards Replies: 5 Views: 2743	Forum: FOR BEGINNERS: What is it? Where is it from? Posted: Feb 06, 2025 13:28 Subject: Re: Unknown banded mineral from shores of lake Buttermere, Cumbria. UK
Pete Richards Replies: 5 Views: 2743	My guess is that it is quartz, based on the appearance of the columns in close-up. It could also be barite or gypsum, which are known to form similar stretch textures.
Topic: Helvine with Quartz or Garnet?
Pete Richards Replies: 17 Views: 5701	Forum: What is it? - Where is it from? Posted: Jan 27, 2025 16:18 Subject: Re: Helvine with Quartz or Garnet?
Pete Richards Replies: 17 Views: 5701	A magnet will tell you if magnetite is present, but I don't see anything that looks like magnetite. As helvine or genthelvite it is much more valuable than garnet!
Topic: Axinite locality in France?
Pete Richards Replies: 3 Views: 2186	Forum: FOR BEGINNERS: What is it? Where is it from? Posted: Jan 07, 2025 17:17 Subject: Re: Axinite locality in France?
Pete Richards Replies: 3 Views: 2186	Here is a suggestive citation from the Axinite page of Mindat: Gautron, Laurent, Meisser, Nicolas (2001) Prehnite from La Combe De La Selle, Saint Christophe-en-Oisans, Isère, France. The Mineralog ...
Topic: Can't read / decode this label to identify the fluorite location...
Pete Richards Replies: 12 Views: 6511	Forum: What is it? - Where is it from? Posted: Nov 26, 2024 11:06 Subject: Re: Can't read / decode this label to identify the fluorite location...
Pete Richards Replies: 12 Views: 6511	Germany (or Austria) certainly seems to make the most sense. As for Switzerland, a Mindat search for "Grube" (mine or pit) with no further locality specification brings up only two matches i ...
Topic: Pezzottaite, new specimens
Pete Richards Replies: 1 Views: 4020	Forum: Minerals and Mineralogy Posted: Oct 19, 2024 17:44 Subject: Re: Pezzottaite, new specimens
Pete Richards Replies: 1 Views: 4020	It appears that the orange color was deposited by growth on the (0001) end faces of the crystal, and perhaps was not deposited at all in the earliest period of growth. The question then becomes, what ...
Topic: what is this? A purple tourmaline grown out from the base of a skeletal quartz?
Pete Richards Replies: 8 Views: 4494	Forum: FOR BEGINNERS: What is it? Where is it from? Posted: Aug 28, 2024 14:11 Subject: Re: what is this? A purple tourmaline grown out from the base of a skeletal quartz?
Pete Richards Replies: 8 Views: 4494	I am sorry, but I think it is very unlikely that the purple prism is amethyst. Perhaps there is a thin film of quartz on the purple mineral that gave a deceptive reading.