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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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 Posted: Mar 15, 2010 12:39 Post subject: Calcite Forms - (4) |
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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
| 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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Elise Skalwold |
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Peter Megaw
Site Admin
Joined: 13 Jan 2007
Posts: 973
Location: Tucson, Arizona
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| Posted: Mar 15, 2010 16:46 Post subject: Re: Calcite Forms - (4) |
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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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crocoite
Joined: 06 Feb 2009
Posts: 490
Location: Ballarat, Victoria
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| Posted: Mar 16, 2010 06:09 Post subject: Re: Calcite Forms - (4) |
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Hi Elise. Here's an Australian calcite for you...club-shaped ferroan calcite from the Bundoora quarry in Melbourne, Victoria. FoV 9mm. Regards, Steve
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5021
Location: Barcelona
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| Posted: Mar 16, 2010 06:40 Post subject: Re: Calcite Forms - (4) |
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Here I am! ;-)
| 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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jorge santos garcia
Joined: 06 Jan 2008
Posts: 34
Location: Évora
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| Posted: Mar 16, 2010 19:24 Post subject: Re: Calcite Forms - (4) |
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Two other complex calcite twins, from Portugal
Cheers
Jorge
| Description: |
Calcite Twin
UNOR 1 - Cruz dos Meninos, Estremoz, Portugal
Crystal size: 11,5 x 6 cm |
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jorge santos garcia
Joined: 06 Jan 2008
Posts: 34
Location: Évora
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| Posted: Mar 16, 2010 19:33 Post subject: Re: Calcite Forms - (4) |
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Forgot add the other one.
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| Calcite twin with manganese oxide inclusions spherules. UNOR 2, Borba, Portugal. Crystal size: 4,5 x 1 cm. |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5021
Location: Barcelona
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| Posted: Mar 17, 2010 05:19 Post subject: Re: Calcite Forms - (4) |
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One more
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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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John S. White
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Joined: 04 Sep 2006
Posts: 1298
Location: Stewartstown, Pennsylvania, USA
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| Posted: Mar 17, 2010 07:54 Post subject: Re: Calcite Forms - (4) |
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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.
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John S. White
aka Rondinaire |
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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| Posted: Mar 17, 2010 10:38 Post subject: Re: Calcite Forms - (4) |
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| 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
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Elise Skalwold |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5021
Location: Barcelona
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| Posted: Mar 17, 2010 10:51 Post subject: Re: Calcite Forms - (4) |
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Are you sure this is Calcite? It looks like a Dolomite (from Spain - Eugui)
Jordi
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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| Posted: Mar 17, 2010 12:57 Post subject: Re: Calcite Forms - (4) |
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| 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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Elise Skalwold |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5021
Location: Barcelona
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| Posted: Mar 17, 2010 14:02 Post subject: Re: Calcite Forms - (4) |
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| Elise wrote: | | ..Do you have a picture of dolomite similar to this which you could post for comparison? |
Here it is
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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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Pete Richards
Site Admin
Joined: 29 Dec 2008
Posts: 842
Location: Northeast Ohio
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| Posted: Mar 17, 2010 18:31 Post subject: Re: Calcite Forms - (4) |
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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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Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Antonio Alcaide
Site Admin
Joined: 23 Aug 2009
Posts: 314
Location: Spain
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| Posted: Mar 17, 2010 20:03 Post subject: Re: Calcite Forms - (4) |
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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
| 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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Life is the shortest crystal |
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GneissWare
Joined: 07 Mar 2008
Posts: 1287
Location: California
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| Posted: Mar 17, 2010 20:57 Post subject: Re: Calcite Forms - (4) |
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Here are a few Calcites for which I have photos.
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Calcite
Berry Materials Quarry
North Vernon
Jennings County, Indiana
United States of America
5.7 x 3.6 cm overall |
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71137 Time(s) |
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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. |
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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 |
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71088 Time(s) |
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