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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5023
Location: Barcelona
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 Posted: Mar 18, 2010 03:34 Post subject: Re: Calcite Forms - (4) |
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| 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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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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| Posted: Mar 18, 2010 16:58 Post subject: Re: Calcite Forms - (4) |
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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
| Description: |
| Red Calcite, Tompkins County, NY, USA, 10.22 x 6.00 x 7.22 mm |
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69881 Time(s) |
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| Description: |
| Red Calcite, Tompkins County, NY, USA 12.50 x 8.32 x 9.50 mm |
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69879 Time(s) |
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| Description: |
| Red Calcite, Tompkins County, NY, USA 10.22 x 6.00 x 7.22 mm |
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69844 Time(s) |
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Elise Skalwold |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5023
Location: Barcelona
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| Posted: Mar 19, 2010 05:20 Post subject: Re: Calcite Forms - (4) |
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And another...
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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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69982 Time(s) |
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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| Posted: Mar 20, 2010 14:38 Post subject: Re: Calcite Forms - (4) |
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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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Elise Skalwold |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5023
Location: Barcelona
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| Posted: Mar 23, 2010 03:25 Post subject: Re: Calcite Forms - (4) |
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| 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
| 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 |
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69945 Time(s) |
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José Miguel
Joined: 09 Apr 2007
Posts: 157
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| Posted: Mar 23, 2010 05:15 Post subject: Re: Calcite Forms - (4) |
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My contribution to the Calcite forms.
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| China, Guiling, Guangxi. 4,5x1,7x1,2 cm |
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38819 Time(s) |
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| Daye, Hubei, China. 8x4,7x2,5 cm |
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38792 Time(s) |
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| Daye, Hubei, China. 7,3x7,5x2,2 cm |
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38839 Time(s) |
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| Milliken (Sweetwater) mine, Viburnum Trend, Reynolds Co., Missouri. 7 x 6,5 x 12 cm |
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38772 Time(s) |
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Carles Curto
Joined: 14 Sep 2006
Posts: 160
Location: Barcelona
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| Posted: Mar 28, 2010 15:36 Post subject: Re: Calcite Forms - (4) |
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| 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. |
To my knowledge the shell is empty and completely buried in a very fine grained mud, in a geological formation very rich in carbonate sediments (probably a shore). The organic part disappears and the walls of the shell operate as a pocket. The calcium of the fossil (it use to be aragonite) operates as a crystallization nucleus and the rest of the calcium necessary to form Calcite is added by the surrounding rock (marl or limestone) permitting the growth of crystals.
Similar processes of mineral growth into a fossil occur with Celestine inside coral, shells or algal formations, and Anapaite and Vivianite inside shells.
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Tobi
Site Admin
Joined: 07 Apr 2009
Posts: 4235
Location: Germany
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| Posted: Mar 29, 2010 03:47 Post subject: Re: Calcite Forms - (4) |
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Hi Elise,
an interesting thread! Calcite is one of the most fascinating minerals and i would say it is among my all-time favourites, together with fluorite, tourmaline, garnet, beryl and quartz. Here are some impressions of calcite crystals from my collection.
Cheers!
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| Typical scalenohedral calcite from Sweetwater Mine, Missouri, USA. The largest one ends in two peaks. Specimen size 10 x 8 x 5 cm. |
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| Reddish calcite scalenohedrons from Rammelsbach Quarry, Palatinate, Germany. Largest crystals in the picture have a lenght of 25 mm. |
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38668 Time(s) |
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| Translucent yellow calcite crystals from La Sambre Quarry near Landelies, Belgium. The largest crystals in the picture have a size of 25 mm. |
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38654 Time(s) |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5023
Location: Barcelona
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| Posted: Mar 29, 2010 11:44 Post subject: Re: Calcite Forms - (4) |
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One more, this time from Spain.
BTW, thanks to Tracy Kimmel for the help in the translation-revision of the Carles Curto text about the "Calcite shell"!
Jordi
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A classic from Spain. Waterclear like Dalnjegorsk, but Spaniard! ;-)
The crystal is very complex and has many faces among which the sharp rhombohedra and shortened scalenohedra stand out, giving it an equidimensional form.
La Florida Mines, La Florida, Cantabria, Spain
Specimen size: 10.5 × 5 × 3.5 cm.
Main crystal size: 2.2 × 2 cm.
Photo: Reference Specimens -> http://www.fabreminerals.com/specimens/RSES-spain-notable-specimens.php#NM46E6 |
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38679 Time(s) |
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38605 Time(s) |
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Tracy
Joined: 15 Sep 2006
Posts: 551
Location: Toronto
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| Posted: Mar 29, 2010 13:00 Post subject: Re: Calcite Forms - (4) |
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My pleasure. :-)
- Tracy
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"Wisdom begins in wonder" - Socrates |
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Tracy
Joined: 15 Sep 2006
Posts: 551
Location: Toronto
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| Posted: Mar 29, 2010 13:04 Post subject: Re: Calcite Forms - (4) |
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By the way, the calcites appearing in this thread are really incredible. I have a weird one of my own to offer but it's really hard to photograph...and not all that attractive...just WEIRD, and with a neat history. I'll keep trying.
- Tracy
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Gerhard Niklasch
Joined: 27 Mar 2009
Posts: 134
Location: Munich
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| Posted: Mar 29, 2010 15:55 Post subject: Re: Calcite Forms - (4) |
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While these buttons may not be all that unusual, they've always struck me as Calcite trying hard (and failing) to pretend to be something else:
``When we grow up, we want to be ....Uvites!''
(Hm, if they were to turn their prisms through 30°, that would be a start...)
Canteras de mármol, Macael, Almería. Andalucía, Spain;
28x24x17mm overall size, acquired in September 2009, collection id 09ESCm001.
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| They come in all sizes here, some frosted, some perfectly smooth... |
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38575 Time(s) |
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| Crossed-eyes stereo pair, field of view 9x15.4mm. |
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38574 Time(s) |
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| Crossed-eyes stereo pair, field of view 12.5x17mm. |
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38665 Time(s) |
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jamesb
Joined: 16 Jan 2010
Posts: 18
Location: Arizona
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| Posted: Mar 29, 2010 22:35 Post subject: Re: Calcite Forms - (4) |
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| I like it ! Esp #3.
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5023
Location: Barcelona
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| Posted: Apr 02, 2010 06:11 Post subject: Re: Calcite Forms - (4) |
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This one from Morocco
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Group of fine laminar crystals of Calcite of hexagonal shape, with color zoning and small recrystallizations of the same Calcite in some areas of the piece.
El Hamman, Meknes Morocco
Specimen size: 9.3 × 5.4 × 4.2 cm.
Main crystal size: 2 × 1.8 cm.
Minor fluorescence long & short UV
Photo: Reference Specimens -> http://www.fabreminerals.com/specimens/RSSLV-silvane-notable-specimens.php#AZ6N4 |
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38497 Time(s) |
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38424 Time(s) |
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Tobi
Site Admin
Joined: 07 Apr 2009
Posts: 4235
Location: Germany
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| Posted: Apr 02, 2010 10:24 Post subject: Re: Calcite Forms - (4) |
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Gerhard, i would like to see more of these stereoscopic pictures. Can you post some more (only if it doesn't trouble you)?
Danke :-)
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