[meteorite-list] Lunar question

[Jerry Flaherty]

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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