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Calcite Forms - (4)
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Elise




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PostPosted: Mar 15, 2010 12:39    Post subject: Calcite Forms - (4)  

Hi!

I was so thrilled by the response to the Smithsonite topic which I hope will continue to grow https://www.mineral-forum.com/message-board/viewtopic.php?t=973&sid=b6b106064a5333c12bcd1fd3f49b5c2c

I hope this calcite topic will have a similar out-pouring of information and beautiful images from member's collections. Along with quartz, I have a fascination with calcite. Until now, all my specimens have been cleavage rhombs, but some are quite special, including a large optical quality one from Iceland which I prize very highly. Another is one with nice chalcopyrite inclusions, a gift from a mineral dealer.

Today, I had the wonderful surprise of receiving the calcite prism I had bought from Jordi. It is exactly what I have been searching for. I am hoping now Jordi and others can tell me more about it, other localities for these and especially what is the horizontal mineral bisecting the prisms and how did it happen? It just came less than 10 minutes ago; I am dying to really study it and take it over to study with my mineralogist friend, but I have to keep working here! So maybe by the time I can visit FMF again, I'll have lots of nice responses to contemplate!

In our museum we have a calcite rhomboid form which I will try to take a picture of to post when I can get a break to do so. If people have the Lithographie 4 Calcite issue, you can see Dr. Mickey Gunter's photograph of a calcite prism, a basal slice and a cleavage rhomb. He also gave the image to me to use in teaching and to post on my website (chronically unfinished), which you can see here: www(dot)nordskip(dot)com(slash)calciteoptics(dot)html Jordi gave me permission to use his picture there also, so I am hoping it is ok to post it here as well

Best wishes,
Elise



calciteprism.jpg
 Description:
Parallel growth of two prismatic crystals, one of them dominant and partially doubly terminated. Second Sovietsky mine, Dal'negorsk, Primorskiy Kray, Russia 6.8 × 4 × 3.1 cm = 2.7” × 1.6” × 1.2” (Photo: Jordi Fabre)
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calciteprism.jpg



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PostPosted: Mar 15, 2010 16:46    Post subject: Re: Calcite Forms - (4)  

First, we have no idea what the orientation of your horizontal substrate was at the time of calcite prism growth. I have seen vein deposits with quartz pseudomorphs after platy calcite crystals (a classic "epithermal vein" texture) with the plates in every imaginable orientation..and later calcites growing perpendicular to the plates. What does seem to matter is that the calcite prism appears to be crystallographically uninterrupted across the substrate, which suggests that there is continuous calcite crystal between the sides and the calcite "ignored" the interference of the plate. This is probably analogous to the genesis of calcite "sand" crystals where the calcite crystallizes continuously in the voids between the sand grains without regard to their presence.

When I get home, I will upload a real poser for this thread...along a similar vein.

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PostPosted: Mar 16, 2010 06:09    Post subject: Re: Calcite Forms - (4)  

Hi Elise. Here's an Australian calcite for you...club-shaped ferroan calcite from the Bundoora quarry in Melbourne, Victoria. FoV 9mm. Regards, Steve


NC-calcite-bundoora-9mm.jpg
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NC-calcite-bundoora-9mm.jpg


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PostPosted: Mar 16, 2010 06:40    Post subject: Re: Calcite Forms - (4)  

Here I am! ;-)


Twinned Calcite Wuzhou Mine China.jpg
 Description:
Twinned Calcite
Wuzhou Mine, Guangxi, China
Mined in October 2007
Specimen size: 2.7 × 2 × 1.5 cm.
Main crystal size: 1.6 × 1.2 cm.
Photo: http://www.fabreminerals.com/specimens/CN-china-mineral-specimens.php#TD46L0
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Twinned Calcite Wuzhou Mine China.jpg


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jorge santos garcia




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PostPosted: Mar 16, 2010 19:24    Post subject: Re: Calcite Forms - (4)  

Two other complex calcite twins, from Portugal

Cheers

Jorge



DSC02046.jpg
 Description:
Calcite Twin
UNOR 1 - Cruz dos Meninos, Estremoz, Portugal
Crystal size: 11,5 x 6 cm
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DSC02046.jpg


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PostPosted: Mar 16, 2010 19:33    Post subject: Re: Calcite Forms - (4)  

Forgot add the other one.


DSC01819.JPG
 Description:
Calcite twin with manganese oxide inclusions spherules. UNOR 2, Borba, Portugal. Crystal size: 4,5 x 1 cm.
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DSC01819.JPG


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PostPosted: Mar 17, 2010 05:19    Post subject: Re: Calcite Forms - (4)  

One more


Calcite with Boulangerite inclusions Herja Roumania.jpg
 Description:
Calcite with Boulangerite inclusions
Herja Mine, Herja, Maramures, Roumania
Mined April 2001
Specimen size: 7 × 4 cm.
Photo: Reference Specimens -> http://www.fabreminerals.com/specimens/RSRO-rumania-notable-specimens.php#E82H
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Calcite with Boulangerite inclusions Herja Roumania.jpg


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PostPosted: Mar 17, 2010 07:54    Post subject: Re: Calcite Forms - (4)  

This is, in my opinion, a very rare twin type from Elwood, Tennessee. This is the only example of this twin that I have seen. Scalenohedral calcites twinned on c(0001) are common at Elmwood. The piece is 7 cm across.


DSCN1623.JPG
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DSCN1623.JPG



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Elise




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PostPosted: Mar 17, 2010 10:38    Post subject: Re: Calcite Forms - (4)  

Peter Megaw wrote:
I have seen vein deposits with quartz pseudomorphs after platy calcite crystals (a classic "epithermal vein" texture) with the plates in every imaginable orientation..and later calcites growing perpendicular to the plates.

Hi Peter, this morning we looked closer at that "horizontal" layer (it is pependicular to the prisms) and it is a platy calcite layer. The prisms are in exactly the same orientation above and below, but different diameter. The pinacoids are bumpy and show the same reflective orientations as the faces of the prisms. So what we thought was that it had all seeded from the platy calcite crystal, growing out from each direction. This was the 5 minute inspection, but would this be along the line of what you are thinking?

I took couple pictures of the calcite form which I mentioned up above which I thought was beautiful. I don't have exact dimensions, but roughly 8 cm on a side.

This is a great thread! Thank you all!
Elise



calcite2.jpg
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calcite2.jpg



calcite1.jpg
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calcite1.jpg



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PostPosted: Mar 17, 2010 10:51    Post subject: Re: Calcite Forms - (4)  

Are you sure this is Calcite? It looks like a Dolomite (from Spain - Eugui)

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PostPosted: Mar 17, 2010 12:57    Post subject: Re: Calcite Forms - (4)  

Jordi Fabre wrote:
Are you sure this is Calcite? It looks like a Dolomite (from Spain - Eugui)

Ouch! Now I am back in my office and can't go check it with someone who would know! Can't always trust these museum tags; they "walk around" with building vibrations from the trucks going by on the road, and I don't know enough about what I am looking at in this case to answer your question. Also, it is separated from its official provenance tag, having been used in a display of the 7 crystal systems with tags to that effect, so I would have to find the archive in storage.

What attracted me to it was that it looked so much like a cleavage rhomb of calcite, except for the twin (if that is called a twin) poking out. I will find out for sure when I go back into the museum. Do you have a picture of dolomite similar to this which you could post for comparison?

This is really quite fascinating to me. I am a gemologist studying mineralogy/crystallography beyond that which is studied as part of the British Gemmological Association's requirements -- which is pretty extensive to the surprise of a mineralogy professor here upon examining my old course materials; and in my case, my instructors were mineralogy professors in Thailand so I gained a bit more than was required. As you know, we "work backwards" from cut material, but I've been studying mineral morphology in the course of inclusion work, that is, studying microscopic crystals inside of other minerals. Having access now to large specimens is really much easier and seeing pictures here has been very helpful. This year, instead of the Sinkankas Symposium, I'll be attending the nearby Rochester Mineralogical Symposium -- I am very much looking forward to that!

Cheers, Elise
PS these calcite prisms are really splendid; did I say that already ;-) ?

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PostPosted: Mar 17, 2010 14:02    Post subject: Re: Calcite Forms - (4)  

Elise wrote:
..Do you have a picture of dolomite similar to this which you could post for comparison?

Here it is



Twinned Dolomite Eugui Navarra Spain.jpg
 Description:
Twinned Dolomite
Azkarate Quarry, Eugui, Navarra, Spain
Specimen size: 4.5 × 3.5 × 2 cm.
Former collection Martín Oliete
Photo: Reference Specimens -> http://www.fabreminerals.com/specimens/SOLI-sold-fine-minerals.php#FL46
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Twinned Dolomite Eugui Navarra Spain.jpg


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PostPosted: Mar 17, 2010 18:31    Post subject: Re: Calcite Forms - (4)  

Certainly Elise's specimen is consistent with the famous dolomite twins from Eugui. But examples of calcite twinned in this morphology are also known. It's worth checking out, but I think the similarity to Eugui dolomite is not conclusive. Simple tests would easily resolve the question, including the rate of fizz in dilute HCl compared to known calcite and dolomite examples.
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PostPosted: Mar 17, 2010 20:03    Post subject: Re: Calcite Forms - (4)  

Hi all,

Here you have my humble contribution. A piece of gem quality crystals of calcite from Hunan as well. It features complex crystals -at least to me- with selective striations -only certain faces show them-.

Regards,
Antonio



calcita.JPG
 Description:
Calcite from Shangbao Pyrite mine, Leiyang Co., Hengyang Prefecture, Hunan Province, China.
11 x 6 cm. Main cristal: 2,5 cm
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calcita.JPG



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PostPosted: Mar 17, 2010 20:57    Post subject: Re: Calcite Forms - (4)  

Here are a few Calcites for which I have photos.


GW000956.JPG
 Description:
Calcite

Berry Materials Quarry
North Vernon
Jennings County, Indiana
United States of America

5.7 x 3.6 cm overall
 Viewed:  42637 Time(s)

GW000956.JPG



GW001083.JPG
 Description:
Calcite

Dalen-Kjørholt Mine
Brevik
Porsgrunn, Telemark Fylke
Norway

11.4 x 6.5 x 6.4 cm overall
4.0 cm Calcite

Specimen possess multiple generations of
Calcite.
 Viewed:  42708 Time(s)

GW001083.JPG



GW000884.JPG
 Description:
Calcite with Wulfenite on Quartz

Red Gem Pocket, North Stope, 120 ft. Level
Red Cloud Open Pit
Silver District
Trigo Mts.
La Paz County, Arizona
United States of America

3.8 x 3.0 x 2.5 cm overall
1.0 cm Calcite
 Viewed:  42631 Time(s)

GW000884.JPG


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PostPosted: Mar 18, 2010 03:34    Post subject: Re: Calcite Forms - (4)  

Pete Richards wrote:
Certainly Elise's specimen is consistent with the famous dolomite twins from Eugui. But examples of calcite twinned in this morphology are also known. It's worth checking out, but I think the similarity to Eugui dolomite is not conclusive. Simple tests would easily resolve the question, including the rate of fizz in dilute HCl compared to known calcite and dolomite examples.

Absolutely!
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PostPosted: Mar 18, 2010 16:58    Post subject: Re: Calcite Forms - (4)  

Hi,
We'll take a look at that calcite/dolomite ID in next few days. Meanwhile today I was helping a friend with samples he just brought back from Pakistan a couple months ago(by way of entering through China) - wonderful cobalt spinel, red spinel and ruby all in matrix, along with red zircon in matrix (Skardu District). Fun to examine. I had to settle for buying some little red calcites which he collected locally (Tompkins County, New York). The Albany museum recently purchased a few larger ones from him. These smaller ones will be more interesting under the microscope, or at least if I put my bifocals on. (#1 and 3 are the same crystal). I am not sure how to orient for the best vantage point.

Elise



redcalcite1.jpg
 Description:
Red Calcite, Tompkins County, NY, USA, 10.22 x 6.00 x 7.22 mm
 Viewed:  42540 Time(s)

redcalcite1.jpg



redcalcite2.jpg
 Description:
Red Calcite, Tompkins County, NY, USA 12.50 x 8.32 x 9.50 mm
 Viewed:  42513 Time(s)

redcalcite2.jpg



redcalcite3.jpg
 Description:
Red Calcite, Tompkins County, NY, USA 10.22 x 6.00 x 7.22 mm
 Viewed:  42490 Time(s)

redcalcite3.jpg



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PostPosted: Mar 19, 2010 05:20    Post subject: Re: Calcite Forms - (4)  

And another...


Calcite replacing Mercenaria sp - Florida USA.jpg
 Description:
A fossilized shell of Mercenaria sp. the interior of which is now occupied by honey-colored Calcite crystals filling most of the available inner space. The Calcite crystals “borrowed” calcium from Mercenarias for their growth.
Ruck's pit, Okeechobee County, Florida, USA
Mined in 2003
Specimen size: 5.3 × 3.3 × 3.6 cm.
Extremely fluorescent long & short UV
Photo: Reference Specimens -> http://www.fabreminerals.com/specimens/RSUS-usa-notable-specimens.php#TA58H2
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Calcite replacing Mercenaria sp - Florida USA.jpg


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PostPosted: Mar 20, 2010 14:38    Post subject: Re: Calcite Forms - (4)  

WoW! Jordi - that is a beautiful natural sculpture and portrait! Does "borrow" imply the calcium of the shell was used up in forming the crystals or does it mean that it acted as a seed crystal for them to form -- and if so, would that mean from the calcite crystal layers or could calcite grow from aragonite layers in the shell? All the pictures in this thread have been really wonderful!

Elise

PS - oh good, the "edit" button is still here! I thought about it longer, maybe a better question is whether this shell is very very old, would it have been in a solution that leached the calcium out of shell and then the crystals formed out of that calcium rich solution? I am completely making this up.

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PostPosted: Mar 23, 2010 03:25    Post subject: Re: Calcite Forms - (4)  

Elise wrote:
...maybe a better question is whether this shell is very very old, would it have been in a solution that leached the calcium out of shell and then the crystals formed out of that calcium rich solution? I am completely making this up.

Elise, I prefer leave the answer for other FMF's members, due my English language level. If you don't get answers, then I would try it myself (bad luck for you if I do it ;-)

I add a new image of another bizarre crystal form of Calcite.

Jordi



Calcite phantom Bou-Azzer.jpg
 Description:
Group of crystals of Calcite formed by two rhombohedrons with evident scalenohedron “phantom” growth inside. The “phantom” is reddish due to a covering layer of Hematite.
Bou Azzer / Agdz, Ouarzazate Morocco
Mined in 2006
Specimen size: 7 × 5.6 × 3.4 cm.
Main crystal size: 1.6 × 1.2 cm.
Intense fluorescence short UV & fluorescent long UV
Photo: Reference Specimen -> http://www.fabreminerals.com/specimens/RSMA-morocco-notable-specimens.php#TR9K9
 Viewed:  42305 Time(s)

Calcite phantom Bou-Azzer.jpg


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