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Magnetic pseudomorph?

Posted by Nik Nikiforou  
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Nik Nikiforou June 01, 2011 01:24AM
A colleague of mine recently received a parcel of minerals from Pakistan which contained several specimens like the one below. The piece is about 6.5 x 5 x 4.5 cm. and the the largest crystal measures 4.3 cm. along an edge. The specific gravity is about 3.6, which matches that of epidote, but it is also weakly magnetic. Is this possibly a pseudomorph of epidote after magnetite, retaining some of the magnetism of the former?
open | download - magep-002.jpg (156.8 KB)
open | download - magep-014.jpg (168 KB)
open | download - magep-021.jpg (169.9 KB)
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Nik Nikiforou June 01, 2011 01:27AM
Here are a couple more photos
open | download - magep-022.jpg (167.3 KB)
open | download - magep-009.jpg (144 KB)
open | download - magep-011.jpg (146.8 KB)
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Mickey Marks June 01, 2011 05:39AM
Your analysis makes sense to me. There could be a partial substitution of epidote for magnetite, with some magnetite still present.
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Peter Haas June 01, 2011 10:04AM
From the close-ups, the material looks very inhomogeneous and part of it appears to be a mixture of fine-grained minerals, possibly with magnetite as one of its constituents.
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Rock Currier June 01, 2011 05:53PM
Those look like some of the new epidotes out of Pakistan.

Rock Currier
Crystals not pistols.
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Nik Nikiforou June 01, 2011 08:17PM
Rock, can you please elaborate? Have you seen these new Epidotes, and if so, do they exhibit a similar "quasi-octahedral" crystal habit? If you have any of the new Epidotes from Pakistan would you mind testing for magnetism?

Thanks,
Nik
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Rock Currier June 02, 2011 10:09AM
OK, here are some of the Pakistani epidotes offed me recently, just fresh from cleaning. Sorry about not putting the pictures here in the body of the message, but when I do I get error messages.

Rock Currier
Crystals not pistols.



Edited 1 time(s). Last edit at 06/02/2011 10:14AM by Rock Currier.
open | download - Epidote, Pakistan 7.JPG (766.6 KB)
open | download - Epidote, Pakistan 2.JPG (812 KB)
open | download - Epidote, Pakistan 3.JPG (867 KB)
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Nik Nikiforou June 02, 2011 12:48PM
Yes, Rock, this is the same material; thanks for your help. Any thoughts on why they are magnetic?

Nik Nikiforou
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Peter Haas June 02, 2011 12:57PM
What is the light green translucent mineral bottom left in the first picture ?
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Rock Currier June 03, 2011 12:11PM
Nick, I have not a clue as to why they might be magnetic. I have not tried it myself. Perhaps there is a little magnetite that has been incorporable into the epidotes as they were growing?

Rock Currier
Crystals not pistols.
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Matt Neuzil June 03, 2011 04:17PM
very nice flat of epidotes!!!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A buena hambre no hay pan duro
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Rock Currier June 03, 2011 07:26PM
I suspect it is epidote as well, perhaps separated a bit from the larger crystal so as to give it more transparency.

Rock Currier
Crystals not pistols.
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Dana Slaughter June 07, 2011 11:30PM
Hello,

I just obtained four of these Pakistani epidote specimens yesterday and observed that mine were magnetic as well. I found a reference to a 1944 paper entitled "The Magnetic Properties of Tourmaline and Epidote" by A. Sigamony. Apparently, this
characteristic isn't as unusual as one might imagine--certainly I never considered magnetism in epidote!

Dana
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Nik Nikiforou June 07, 2011 11:45PM
Good find Dana! Here's a link to an abstract of that article:

Article abstract

By the way, do you have a specific locality for your specimens?

Thanks,
Nik Nikiforou
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Dana Slaughter June 08, 2011 02:09AM
Hi Nik,

Yes, the nearest town or city to the presumed locality (being kept somewhat secret at the moment) is Quetta, Balochistan (Baluchistan), Pakistan. I was quite surprised to find that my specimens were mildly to moderately magnetic and I was unaware of any reaction to a magnet with the mineral. I think that these are fabulous specimens--especially to all of us dark mineral-addicted collectors out there! I hope all is well and I wish you continued success!

Take care,
Dana
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Steve Hardinger June 08, 2011 04:29AM
Maybe someone can sacrifice a lesser quality specimen from this lot to the saw...maybe they have epidote skin over magnetic core?
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Rock Currier June 08, 2011 04:04PM
I will hopefully be getting a bunch of them soon and if there is anyone out there interested in working on these, Ill happily provide one for science.

Rock Currier
Crystals not pistols.
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Nik Nikiforou June 09, 2011 06:18PM
According to the 1944 article abstract mentioned above, the inherent magnetism of the epidote is due to a ferrous oxide content of 4% to 17% compared to less than 1% in the non-magnetic samples, so I would not expect any actual magnetite to be hidden inside the specimen. I only mentioned magnetite in my original question because of the unusual octahedral shape of the crystals, which I have never seen in Epidote before.
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Michael Hatskel June 09, 2011 09:27PM
Nik,
Please double-check: the abstract you are referencing (actually the intro portion of the paper) says 4-17% ferric oxide, i.e. Fe2O3, not ferrous oxide FeO.
Epidote occurs together with magnetite so often that it should not be very difficult to imagine microcrystals of magnetite included in such large epidote crystals. Could it be that as a later formed mineral, epidote incorporated some earlier formed magnetite crystals?

Also, does your specimen show magnetism all way around it or it is localized in some spots?
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Rob Woodside June 09, 2011 09:44PM
I think ferrous iron subs for Ca in epidote structure, so there is some hope for magnetic epidote sans magnetite.
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Michael Hatskel June 09, 2011 11:28PM
Rob,
It may be possible, if 1-2%wt FeO is sufficient for creating a weak but perceptible magnetism.
I just don't know if that is sufficient.
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Nik Nikiforou June 10, 2011 12:36AM
The piece that I have seems to be uniformly magnetic on all surfaces.
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gary moldovany June 10, 2011 01:41AM
Nice specimens! I would like to get one for my collection. Can anyone point me in the right direction? Thanks. Gary
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Nauroz Nausherwani January 12, 2012 10:04PM
The correct locality of these specimens is Raskoh Mountain Range, Kharan,Balochistan,Pakistan. These specimens are found in the sand on the mountains of this Raskoh( the name of mountain is local Balochi Language) mountain range.

I will soon going be for collecting these specimens . I will post locality pictures in my mindat gallery so they can help you people. Keep visiting my mindat gallery.


Nauroz Nausherwani
Nausherwani Mines, Kharan,Balochistan
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Reiner Mielke January 13, 2012 01:28AM
I broke a magnetic octahedral epidote crystal open and there is no magnetite inside or any sign of included magnetite under 60X. The crystal could be picked up by a magnet very easily.



Edited 1 time(s). Last edit at 01/13/2012 02:10PM by Reiner Mielke.
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Rock Currier January 13, 2012 08:49AM
The epidotes from this locality appear to very considerably on how magnetic they are. We (Rock Currier/Jewel Tunnel Imports) got a lot of about 2 to 300 specimens. Some of them you could actually pick up with a magnet. Others would attract a magnet on a string and yet others there appeared to be no attraction at all. I sent a sample of the magnetic epidote to a friend with access to equipment and he said when he had time he would make some thin sections and then scan them with a microprobe and see if he could resolve any magnetic inclusions in the material. As yet, no answers.

Rock Currier
Crystals not pistols.
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Nauroz Nausherwani January 13, 2012 10:52AM
Its an interesting issue . I came to know about this discussion from my friend when we were talking about the same topic on Mindat chatroom.

ROck Currier please inform us when you got reply from your friend.

Nauroz Nausherwani
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Johan Kjellman January 13, 2012 01:20PM
Aren't these nice?
Be aware though, that the "magnetism" referred to in the article is paramagnetism as opposed to the ferromagnetic properties that the pakistani epidotes exhibit.
I got a couple of crystals in Munich and there are both magnetic and nonmagnetic crystals around.
Some dealers in munich used the magnetic properties and the "unusal" octahedral morphology as a sales pitch for promoting the crystals. Others called them pseudomorphic after magnetite, referring to the "octahedrons" as showing the outer morphology of the "original" mineral magnetite.
This is of course not true as the octahedral morphology of these epidotes doesn't display any cubic symmetry.
My conclusion from the above facts are that they are "just" epidotes with a somewhat unusual morphology, carrying inclusions of a ferromagnetic mineral, magnetite? being the most likely candidate, in proportions from zero and upwards.

cheers



Edited 1 time(s). Last edit at 01/13/2012 03:29PM by Johan Kjellman.
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Harald Schillhammer January 13, 2012 04:26PM
I also recently obtained two specimens of those epidotes and, curious as I am, viewed one of those big chunks under the microscope. The surface is powdered with numerous tiny, bright greenish (2nd generation?) epidotes and zillions of microscopic cavities, many of them containing a corroded-looking metallic mineral, maybe the magnetite in question. The distribution is quite uneven, though.

Here's a rough and dirty photo of the surface (FOV ca. 10mm) - click on the image for a larger and sharper view:

http://www.pbase.com/rovebeetle/image/140888810/original.jpg

Cheers

Harry



Edited 1 time(s). Last edit at 01/13/2012 04:28PM by Harald Schillhammer.
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Nik Nikiforou January 13, 2012 05:14PM
The August 2011 issue of Mineral News has an article on this deposit of Epidote:

http://www.mineralnews.com/backissue_11.htm

I haven't read it but in a conversation with Tony Nikischer he told me that tiny particles of Magnetite were found inside of the crystals. I'm not sure what kind of analysis was done, but I'm sure that the article goes into detail on that.

Best regards,
Nik
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Lloyd Van Duzen January 15, 2012 03:31AM
Wow, love the material in question and the thread is interesting as well. Nice.
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Nauroz Nausherwani February 24, 2012 07:33PM
Hi Mindat,
To my recent visit to these Epidote deposits at Luss,Raskoh Mountain,Kharan,Balochistan I have found that the whole Raskoh Mountain is made of Granite and magnetite is present in the Granite. So I became certain that epidote from this locality is magnetic because of mother rock Granite with magnitite. Take a look at locality pictures on
http://www.mindat.org/user-13658.html#2
and video at

http://www.youtube.com/watch?v=2RuX4AgQHqM

Thanks,

Nauroz Nausherwani
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Nauroz Nausherwani February 24, 2012 07:33PM
Hi Mindat,
To my recent visit to these Epidote deposits at Luss,Raskoh Mountain,Kharan,Balochistan I have found that the whole Raskoh Mountain is made of Granite and magnetite is present in the Granite. So I became certain that epidote from this locality is magnetic because of mother rock Granite with magnitite. Take a look at locality pictures on
http://www.mindat.org/user-13658.html#2
and video at

http://www.youtube.com/watch?v=2RuX4AgQHqM

Thanks,

Nauroz Nausherwani
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Robert Simonoff February 25, 2012 01:48AM
We spoke with Dudley Blauet of Mountain Minerals about these epidotes last August. He has had them analyzed and found them to contain varying amounts of magnetite inclusions. He was hoping someone would retest them to validate the results his lab obtained.

Bob
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Bill Wall February 25, 2012 02:06AM
so what are you calling them epidote or magnetite xls ?? bill
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Robert Simonoff February 25, 2012 02:55AM
I would go with epidote with magnetite inclusions personally.

Bob
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Alfredo Petrov February 25, 2012 03:32AM
I agree with Bob: epidote with millions of microscopic magnetite inclusions. I see no evidence pointing to pseudomorphs. confused smiley

Very weird stuff; get them while they last (no, I don't have any). sad smiley
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R. Peter Richards February 25, 2012 03:45PM
I'm not an expert on this, but I think that article is not talking about the kind of magnetism that we normally think of - or at best it would be so weak that it would require special instruments to detect it, not just a magnet.
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Nik Nikiforou February 25, 2012 04:55PM
No special instruments needed, just a strong magnet (see photo). Everyone of these that I've tested (about a dozen different specimens from various dealers) is weakly magnetic.
open | download - kgepy03-001.jpg (147.9 KB)
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José Zendrera February 26, 2012 01:40AM
I have my own specimen of epidote from this locality, also magnetic. I checked Specific Gravity of my specimen: 3,8. Epidote SG range is 3,3 - 3,5 depending on the iron content. We can suppose that pure Raskoh’s epidote should have max iron content and his SG is 3,5. The weight excess must be due to magnetite inclusions. As magnetite SG is 5,2, is easy to calculate there is 12% of magnetite included in these epidote crystals, provided that no other mineral is present. Epidote and magnetite are commonly associated but never had been arrived at this point!

Nauroz, very thanks for posting your Raskoh Mts. locality pics, are very interesting and instructive showing geological details. In pictures can see many types of rocks from granite to limestone and several grade metamorphic rocks, some with metasomatic mineralization. Please let me comment some of your photos:


This look sedimentary rocks, perhaps limestone or sandstone with some grade of metamorphism. Cyclic stratification appears to show flysh type sediments alternating hard and soft materials.



Here can see dark metamorphic rocks crossed by granite or diorite intrusions, all well stirred and folded. Please let me know if the find is near the contact between both rocks.



That look as metamorphic flysh materials but granite is not far at all as seen behind them.


Jose
open | download - R1.jpg (246.9 KB)
open | download - R2.jpg (378.5 KB)
open | download - R3.jpg (423.3 KB)
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José Zendrera February 26, 2012 01:59AM
This looks the result of a metasomatic process in contact metamorphism whereby iron and calcium are provided by the sedimentary rocks transforming the quartz and feldspar of igneous intrusive front to form epidote and magnetite. White matrix could be feldspar remnants; the rest of metasomatic skarn process should be mica group minerals easily weathered facilitating the collection of the epidote.


Graphic demonstration of the magnetic properties:


Epidote - clinozoisite, diopside and magnetite from unknown locality also in Pakistan (received without label as a gift from a Pakistani dealer). This is an alpine type growth, completely different to metasomatic transformation origin of related magnetic pseudo-octahedral Raskoh epidote.


Jose



Edited 2 time(s). Last edit at 02/26/2012 02:56AM by Jose Zendrera.
open | download - R4.jpg (363.5 KB)
open | download - epi_2.JPG (254.9 KB)
open | download - epimag.JPG (399.1 KB)
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