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Magnetic pseudomorph?

Posted by Nik Nikiforou  
Magnetic pseudomorph?
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?
Attachments:
open | download - magep-002.jpg (156.8 KB)
open | download - magep-014.jpg (168 KB)
open | download - magep-021.jpg (169.9 KB)
Re: Magnetic pseudomorph?
June 01, 2011 01:27AM
Here are a couple more photos
Attachments:
open | download - magep-022.jpg (167.3 KB)
open | download - magep-009.jpg (144 KB)
open | download - magep-011.jpg (146.8 KB)
avatar Re: Magnetic pseudomorph?
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.
avatar Re: Magnetic pseudomorph?
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.
avatar Re: Magnetic pseudomorph?
June 01, 2011 05:53PM
Those look like some of the new epidotes out of Pakistan.

Rock Currier
Crystals not pistols.
Re: Magnetic pseudomorph?
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
avatar Re: Magnetic pseudomorph?
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.
Attachments:
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)
Re: Magnetic pseudomorph?
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
avatar Re: Magnetic pseudomorph?
June 02, 2011 12:57PM
    
What is the light green translucent mineral bottom left in the first picture ?
avatar Re: Magnetic pseudomorph?
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.
avatar Re: Magnetic pseudomorph?
June 03, 2011 04:17PM
    
very nice flat of epidotes!!!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A buena hambre no hay pan duro
avatar Re: Magnetic pseudomorph?
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.
avatar Re: Magnetic pseudomorph?
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
Re: Magnetic pseudomorph?
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
avatar Re: Magnetic pseudomorph?
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
avatar Re: Magnetic pseudomorph?
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?
avatar Re: Magnetic pseudomorph?
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.
Re: Magnetic pseudomorph?
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.
Re: Magnetic pseudomorph?
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?
avatar Re: Magnetic pseudomorph?
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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