[meteorite-list] NWA 6709 - iridescence

From: James Baxter <jbaxter112_at_meteoritecentral.com>
Date: Thu, 21 Jul 2011 15:04:20 -0400
Message-ID: <2049367696.3868491311275059989.JavaMail.root_at_zmcs01l-pol-08.portal.webmd.com>

Pure speculation but my guess is that the rainbow sheen comes from refraction due to some fine layering of material on the surface. In the case of fresh unweathered falls it is almost certainly a phenomenon related to the crust formation itself but one could imagine weathering causing a similar effect due to thin layers of oxide or other weathering product.

So maybe similar effect with two different causes??

In Martin and Stefans' case, seems more likely to be a primary crust related finding in a minimally weathered desert find rather than due to weathering, but again just speculation

Jim Baxter


----- Original Message -----
From: "Marc Fries" <mfries8 at hotmail.com>
Cc: meteorite-list at meteoritecentral.com
Sent: Thursday, July 21, 2011 10:47:39 AM GMT -08:00 US/Canada Pacific
Subject: Re: [meteorite-list] AD: Special: Truly baffling & sensational Howardite - NWA 6709 - iridescence

That brings up a good question, then - is this iridescence the result of
weathering, or does it come from heating? Either could cause mild
oxidation. I had assumed that the iridescence I saw in basalts came
from weathering, but perhaps it was a consequence of heating. Basalt
gets plenty hot. :-) I like this discussion. Thoughts?

On 7/21/11 10:12 AM, James Baxter wrote:
> There is sometimes a similar though less dramatic iridescence on the crust of newly fallen ordinaary chondrites that have not been exposed to significant weathering.
>
> Jim Baxter
>
>
> ----- Original Message -----
> From: "Marc Fries"<mfries8 at hotmail.com>
> To: meteorite-list at meteoritecentral.com
> Sent: Thursday, July 21, 2011 9:53:21 AM GMT -08:00 US/Canada Pacific
> Subject: Re: [meteorite-list] AD: Special: Truly baffling& sensational Howardite - NWA 6709 - absolutely stunning and very fresh.
>
> Mild oxidation of silicate glass (fusion crust in this case) can produce
> a rainbow effect, too. I've seen this in basalts in the field. I think
> it is from a sheen of iron oxides created as the iron and/or sulfide
> weathers out.
>
> Cheers,
> Marc Fries
>
> On 7/21/11 1:13 AM, Aubrey Whymark wrote:
>> Hi
>>
>> The rainbow colour looks like oil to me. Maybe someone has used oil or WD40 to clean it. I sometimes encounter 'rainbow' tektites and the guys want extra because of it - in reality it is due to oil contamination, probably from the mining operations.
>>
>> Regards, Aubrey
>> www.tektites.co.uk
>>
>>
>>
>> --- On Thu, 21/7/11, Martin Altmann<altmann at meteorite-martin.de> wrote:
>>
>>> From: Martin Altmann<altmann at meteorite-martin.de>
>>> Subject: Re: [meteorite-list] AD: Special: Truly baffling& sensational Howardite - NWA 6709 - absolutely stunning and very fresh.
>>> To: meteorite-list at meteoritecentral.com
>>> Date: Thursday, 21 July, 2011, 0:33
>>> Hi Mike,
>>>
>>> no worries, neither we understood it like that.
>>>
>>> Of course, if one looks to the photos, the first idea,
>>> which comes to one's
>>> mind is: oil.
>>> No idea, what causes this effect, maybe the composition.
>>> Also that strange
>>> tint the cut faces reveal.
>>>
>>> And especially worrying is the variety of the odd
>>> inclusions. I mean
>>> normally we all get already excited, whenever we find a
>>> carbonaceous
>>> fragment in a howardite,
>>> but what that stone has all for strange clasts - that is
>>> really not normal
>>> anymore.
>>>
>>> Since 1999 Stefan is in Morocco and since then we certainly
>>> had quite a
>>> bunch of materials in our hands,
>>> but such a weird polymict one - extremely unusual.
>>>
>>> And it seems that many collectors feel the same, if after
>>> such a short time
>>> now only three slices are left.
>>>
>>> Now all of the smaller ones are gone, sorry for that. But
>>> we have still a
>>> slice left, which we could subdivide into small partslices,
>>> if desired - but
>>> for that one has really to raise his finger.
>>>
>>> For the moment!
>>> Martin
>>>
>>> -----Urspr?ngliche Nachricht-----
>>> Von: meteorite-list-bounces at meteoritecentral.com
>>> [mailto:meteorite-list-bounces at meteoritecentral.com]
>>> Im Auftrag von Galactic
>>> Stone& Ironworks
>>> Gesendet: Donnerstag, 21. Juli 2011 00:48
>>> An: Chladnis Heirs
>>> Cc: meteorite-list at meteoritecentral.com
>>> Betreff: Re: [meteorite-list] AD: Special: Truly baffling
>>> & sensational
>>> Howardite - NWA 6709 - absolutely stunning and very fresh.
>>>
>>> Hi Martin,
>>>
>>> I didn't mean to impeach the meteorite, I was just
>>> curious.
>>>
>>> This is indeed a mystery. Have any scientists offered
>>> or agreed to
>>> look at it? Perhaps hit the rainbow area with the
>>> microprobe or SEM?
>>>
>>> Aesthetically speaking, it's gorgeous and looks like Mother
>>> of Pearl. :)
>>>
>>> Best regards,
>>>
>>> MikeG
>>>
>>> --
>>> ----------------------------------------------------------------------------
>>> -----
>>> Galactic Stone& Ironworks - Meteorites& Amber
>>> (Michael Gilmer)
>>>
>>> Website - http://www.galactic-stone.com
>>> Facebook - http://tinyurl.com/42h79my
>>> News Feed - http://www.galactic-stone.com/rss/126516
>>> Twitter - http://twitter.com/galacticstone
>>> EOM - http://www.encyclopedia-of-meteorites.com/collection.aspx?id=1564
>>> ----------------------------------------------------------------------------
>>> -----
>>>
>>> On 7/20/11, Chladnis Heirs<news at chladnis-heirs.com>
>>> wrote:
>>>> No, it's natural!
>>>>
>>>> Martin
>>>>
>>>>
>>>> -----Urspr?ngliche Nachricht-----
>>>> Von: Galactic Stone& Ironworks [mailto:meteoritemike at gmail.com]
>>>> Gesendet: Mittwoch, 20. Juli 2011 23:24
>>>> An: Chladnis Heirs
>>>> Cc: meteorite-list at meteoritecentral.com
>>>> Betreff: Re: [meteorite-list] AD: Special: Truly
>>> baffling& sensational
>>>> Howardite - NWA 6709 - absolutely stunning and very
>>> fresh.
>>>> Wow! That is one of the most beautiful
>>> howardites I have ever seen.
>>>> Nice find. :)
>>>>
>>>> The rainbox coloration is very odd. Was the
>>> stone cleaned at any time?
>>>> Best regards,
>>>>
>>>> MikeG
>>>>
>>>>
>>> ----------------------------------------------------------------------------
>>>> -----
>>>> Galactic Stone& Ironworks - Meteorites&
>>> Amber (Michael Gilmer)
>>>> Website - http://www.galactic-stone.com
>>>> Facebook - http://tinyurl.com/42h79my
>>>> News Feed - http://www.galactic-stone.com/rss/126516
>>>> Twitter - http://twitter.com/galacticstone
>>>> EOM - http://www.encyclopedia-of-meteorites.com/collection.aspx?id=1564
>>>>
>>> ----------------------------------------------------------------------------
>>>> -----
>>>>
>>>> On 7/20/11, Chladnis Heirs<news at chladnis-heirs.com>
>>> wrote:
>>>>> Dear meteorite community,
>>>>>
>>>>> with this Special we have to introduce to you an
>>> enormous oddity.
>>>>> It is about a HED-meteorite of a kind, which we
>>> hadn't ever seen before
>>> in
>>>>> our careers before.
>>>>>
>>>>> It came in two stones, one of them was covered
>>> with a lush fusion crust,
>>>>> wonderfully structured by thick and oriented
>>> flowlines.
>>>>> And in some parts, that very crust displayed a
>>> gloss and a shine,
>>>> iridescent
>>>>> in all colours of the rainbow;
>>>>> an effect, reminding almost to bismuth!
>>>>>
>>>>> Please take a look to the photos, where we tried
>>> to captured the effect:
>>>>> http://www.chladnis-heirs.com/new-meteorites/nwa6709.html
>>>>>
>>>>>
>>>>> The interior was no less a riddle for us.
>>>>> The distribution and sizes of the various
>>> fragments and clasts were
>>> unlike
>>>>> we had seen in any polymict HED before.
>>>>> A variety of clasts is of a kind, like we never
>>> had recovered in any
>>> Vesta
>>>>> meteorite. Please take a closer look to the slices
>>> and you will share our
>>>>> surprise.
>>>>>
>>>>> And a very few of these clasts develope due to
>>> their microscopically
>>>>> lamellae-texture a fire like an opal, if turned
>>> around in the light.
>>>>> The response to a magnet is very inhomogeneous
>>> within the slices,
>>>>> although no differences are visible to the eye
>>>>> and all in all the interior has a somewhat dull
>>> yellowish tint - although
>>>>> the material is very fresh - and that tint and the
>>> circumstances made us
>>>>> initially think, it might be diogenitic.
>>>>>
>>>>> It is under classification at Dr. Anthony Irving
>>> and the values say, that
>>>> it
>>>>> is a shocked howardite.
>>>>>
>>>>> We crafted now a set of polished sliced of all
>>> sizes, to share this
>>>>> exceptional material with you.
>>>>> Please acknowledge that we have kept the price,
>>> despite of the for us so
>>>>> unique properties of the material, well
>>> affordable,
>>>>> for everybody staying able to add a specimen of
>>> this truly exceptional
>>>> stone
>>>>> to his collection.
>>>>> And an addition it is, also for the most
>>> experienced veteran collector.
>>>>> Earlier today we had published the Special in the
>>> German forum, therefore
>>>>> not so many specimens are left.
>>>>>
>>>>> For the largest slice we can offer a discount as
>>> it is the only one,
>>> which
>>>>> isn't coplanar.
>>>>>
>>>>> And finally, the specimen named "piece #2", which
>>> we chose to illustrate
>>>>> best that rainbow-bismuth-gloss of the fusion
>>> crust on the first linked
>>>>> page, is available too. It weighs 119.2g and we're
>>> accepting offers.
>>>>> Here you are now:
>>>>> http://www.chladnis-heirs.com/specials/special-nwa6709.html
>>>>>
>>>>>
>>>>> Best Regards,
>>>>> Stefan& Martin
>>>>>
>>>>> Chladni's Heirs
>>>>> Munich - Berlin
>>>>> Fine Meteorites for Science& Collectors
>>>>>
>>>>> http://www.chladnis-heirs.com
>>>>>
>>>>>
>>>>>
>>>>> ______________________________________________
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>>>>> http://www.meteoritecentral.com/mailing-list-archives.html
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>>>>>
>>>> --
>>>>
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Received on Thu 21 Jul 2011 03:04:20 PM PDT