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Kidwellite : NaFe3+9+x(PO4)6(OH)11·3H2O, x = 0.33, Natrodufrénite : NaFe2+Fe3+5(PO4)4(OH)6·2H2O

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minID: E9A-EKJ

Kidwellite : NaFe3+9+x(PO4)6(OH)11·3H2O, x = 0.33, Natrodufrénite : NaFe2+Fe3+5(PO4)4(OH)6·2H2O

This image is copyrighted. Unauthorized reproduction prohibited.
Field of View: 3 mm

Zoned kidwellite from the old Indian Mountain locality north of the extinct town of Bluffton, Cherokee County, Alabama. Blue-green core and thin intermediate layers is natrodufrénite. Radial aggregate split exactly at the plane of nucleation of the natrodufrénite.
Such (epitaxial) intergrowths of kidwellite and natrodufrénite are common also in other localities since both species have similar crystal structures.

FOV is about 2.5 X 2 mm. Canon 40D with a 48mm B&L objective, bellows configuration and fluorescent ring light. Stacked using Combine ZP.

Collected: 1967

This Photo was Mindat.org Photo of the Day - 2nd Apr 2016

This photo has been shown 964 times
Photo added:20th Dec 2015
Dimensions:1024x765px (0.78 megapixels)
Date/Time of Photo:19th Dec 2015 23:20:24
Camera:CANON EOS 40D
Software:CombineZP
Exposure time:1/20s
ISO speed:400
View Henry Barwood's Photos View Kidwellite Gallery

Discuss this Photo

PhotosKidwellite - Indian Mountain, Cherokee Co., Alabama, USA

2nd Apr 2016 21:27 BSTJim Robison

Henry


I don't know the phosphates at all, and am totally unfamiliar with the minerals pictured. But it is a very striking and interesting photograph and I have a question about your explanation. When I enlarge the pic, it appears that the light blue ring recurs a number of times. Is that so, since you reference only the central core? I don't understand the reference to an aggregate structure. For a simple guy who only really knows the carbonate minerals, I'd appreciate learning something new. Great picture by the way, a real triumph for you to capture this with such precision.


Jim

2nd Apr 2016 21:43 BSTUwe Kolitsch Manager

Caption edited.

3rd Apr 2016 01:44 BSTHenry Barwood Expert

The nuclei of these aggregates is natrodufrenite (XRD and EPMA analyzed) the color variations are from oxidation state of the Fe. The yellow green fibers that dominate the radial aggregate are kidwellite (again both XRD and EPMA analysis). I did a study 20 years ago of dozens of dufrenite and kidwellite specimens from worldwide locations and determined that only a small number of "dufrenite" specimens were actually dufrenite (Ca dominant). All the others were indeed natrodufrenite (XRD and EPMA). The study was never published, but I can assure you my data is accurate!


From the point of nucleation, you have several blue-green bands of natrodufrenite followed by a thin band of kidwellite (Na depletion of the fluids?) followed by another band of natrodufrenite. The rest of the specimen is kidwellite with color variations caused by Fe++/Fe+++ oscillation.

3rd Apr 2016 02:08 BSTKeith Compton Manager

Henry

Perhaps you could include your report here on Mindat as a member article

I suggest that it would make an interesting read and maybe lead to numerous corrections around the world

Cheers

Keith

3rd Apr 2016 02:27 BSTHenry Barwood Expert

Keith,


Thanks, but little likelihood that I would be able to do this. No longer have adequate access to a laboratory or a library to complete a technical paper.

3rd Apr 2016 21:59 BSTJim Robison

Henry


Thanks for the information. Never had any doubt about your qualifications or conclusions, hope none was generated. I am just curious about the wonders of the mineral world, and learned some new things today. Fascinating. A very cool little rock, and amazingly complex. I am almost a complete newbie to effect of iron oxidation states on color. Must have been a constantly changing fluid depositing, with minute changes is solution chemistry. My only previous experience with iron oxidation states was over 40 years ago at an abandoned very old mine in Virginia, where clear water was issuing from a crack on the surface in a thin stream down the slope, and I watched the iron in solution oxidize over a period of several inches. Impressed me on the rate at which solution chemistry can change in just a few seconds.
 
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