[meteorite-list] Lunar question

From: Jerry Flaherty <grf2_at_meteoritecentral.com>
Date: Fri, 4 Sep 2009 20:16:28 -0400
Message-ID: <350B237B8DE843FDA27625425768864D_at_ASUS>

Thanks Dennis for the question and Randy for a clear summary.
Jerry Flaherty

--------------------------------------------------
From: "Randy Korotev" <korotev at wustl.edu>
Sent: Friday, September 04, 2009 2:10 PM
To: <meteorite-list at meteoritecentral.com>
Subject: Re: [meteorite-list] Lunar question

> Dennis:
>
> I might be able to answer your question, but I need to understand the
> question better.
>
> Do you mean "breccia basalt" as opposed to just "breccia?" Most lunar
> meteorites are breccias, but only a few of the breccias are basaltic.
> Most basaltic lunar meteorites are not breccias; they're unbrecciated
> basalts. Did you follow that?
>
> In my opinion, in the absence of a fusion crust it's impossible to
> identify a lunar meteorite "just by looking," and I've seen practically
> all of them. I have bought or been sent about 4 alleged lunar meteorites
> from experienced collectors and dealers in the past 5 years that turned
> out to be terrestrial rocks, eucrites, or howardites. I've seen some
> lunar meteorites, most notably the Kalahari stones, that don't look
> anything like a moon rock or a any kind of meteorite.
>
> Some, if not many, terrestrial basalts "look like" martian and lunar
> basaltic meteorites. So far, none of the lunar or martian basaltic
> meteorites are as vesicular as are many terrestrial basalts, but lack of
> vesicles sure doesn't make it a planetary meteorite. A chemical or
> mineralogical analysis is neede to distiguish among terrestrial, martian,
> lunar, and asteroidal basalts.
>
> They're are some kinds of terrestrial rocks that strongly resemble lunar
> breccias. Several people have sent me ignimbrites (alias ash-flow tuffs
> or, more generically, volcaniclastic rocks) that look like lunar breccias.
> There are also types of sedimentary processes on earth that can lead to
> impact-breccia look-alikes.
>
> http://meteorites.wustl.edu/meteorwrongs/m118.htm
> http://meteorites.wustl.edu/meteorwrongs/m151.htm
> http://meteorites.wustl.edu/meteorwrongs/m156.htm
> http://meteorites.wustl.edu/meteorwrongs/m159.htm
> http://meteorites.wustl.edu/meteorwrongs/m195.htm
> http://meteorites.wustl.edu/meteorwrongs/m200.htm
> http://meteorites.wustl.edu/meteorwrongs/m216.htm
> http://meteorites.wustl.edu/meteorwrongs/m219.htm
> http://meteorites.wustl.edu/meteorwrongs/m225.htm
> http://meteorites.wustl.edu/meteorwrongs/m235.htm
> http://meteorites.wustl.edu/meteorwrongs/m237.htm see this one,
> especially
> http://meteorites.wustl.edu/meteorwrongs/m260.htm
> http://meteorites.wustl.edu/meteorwrongs/m279.htm
>
> Some porphyritic basalts resemble lunar breccias to the untrained eye.
>
> http://meteorites.wustl.edu/meteorwrongs/m086.htm
> http://meteorites.wustl.edu/meteorwrongs/m129.htm
> http://meteorites.wustl.edu/meteorwrongs/m259.htm
>
> With regard to the breccias, here are some things to look for:
>
> Aspect ratios of clasts in lunar breccias are practically never greater
> than 3 to 1.
>
> There is practically no preferred orientation of clasts in a lunar (or
> asteroidal) breccia. Preferred orientation requires gravity (or flow,
> which might happen in an impact-melt breccia, but is rare).
>
> Clasts are mostly angular, with only a bit of rounding on some. All
> rounding is caused by impact abrasion, which isn't nearly as efficient as
> rocks being tumbled by moving water.
>
> Clasts don't have rims and cores of any kind, except maybe from
> terrestrial weathering processes.
>
> If a clast is layered, it's not from the Moon. Layered rocks require
> gravity and air or water.
>
> Lunar breccias are remarkably uncolorful - just shades of gray. Nearly
> all the lunar meteorites from Oman are stained by hematite, however,
> causing reddish regions. The NWA stones (interior) are less colorful.
>
> Clast in lunar breccias never have geometric shapes like prisms,
> rectangles, etc.
>
> Most brecciated lunar meteorites are regolith breccias. These often have
> white clasts of anorthosite in a dark matrix of lithified soil. Impact
> melt and granulitic breccias are rarer and are remarkably unremarkable
> (sawn surface).
>
> Hope this helps.
>
> Randy Korotev
>
>
>
>
> At 10:38 04-09-09 Friday, you wrote:
>
>>Good Morning All... I have a rather novice question: What is the
>>identifying
>>tag or indicator that differentiates a Lunar breccia basalt from a
>>terrestrial
>>breccia? I have cut and examined several that I have found, and not
>>knowing the difference, made coasters out of them... I know you guys that
>>run to Morocco to purchase them, from time to time, have a good idea
>>without
>>taking a lab with you....
>> Thanks!
>>Dennis Miller
>>
>>Sorry, nothing to give away, but bare with me.....
>>Oh, I did give one of my non-lunar coasters to Haag.
>
> Randy Korotev
> Saint Louis, MO
> korotev at wustl.edu
>
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Received on Fri 04 Sep 2009 08:16:28 PM PDT