Greg;
Most lunar rocks are impact breccias - rocks made up of bits and
pieces of older rocks. The pieces are called clasts and they may be
suspended in a matrix of crystallized impact melt, glass, or
shocked-compressed smaller clasts. Big clasts are fragments of
rocks. The smaller clasts are typically single mineral grains. It's
not uncommon to see clasts of "breccias in breccias in
breccias." Often, the clasts are cracked and bent as a result of
shock (visible in thin section). These effects also destroy the
transparency. It would be rare to see an attractive mineral clast
with a hand lens on the broken surface of a lunar breccia. Keep in
mind that the ancient lunar highlands is ~80% plagioclase and the
rest is mainly pyroxene and olivine. Plag doesn't take well to being
beat up. You're most likely to see an olivine crystal, but it won't
be very big.
There are two coarse-grained basalts among the lunar meteorites,
almost certainly source-crater paired.
http://meteorites.wustl.edu/lunar/stones/mil05035.htm
http://meteorites.wustl.edu/lunar/stones/asuka881757.htm
They show little evidence of having been affected by impacts (other
than the obvious - they were found on Earth!). As a consequence,
they have big crystals, by lunar standards.
Small olivine grains are obvious on NWA032/479
http://meteorites.wustl.edu/lunar/stones/nwa0032.htm
Oh, and a petrographically inclined colleague reminded me yesterday
that it's "crossed nicols," not "nichols," and that the metal in
lunar breccias is, in fact, crystalline, though a bit opaque.
Randy Korotev
At 06:19 PM 2010-12-29 Wednesday, you wrote:
Thank you Larry - Sometimes you just can't get your thoughts to the
fingertips.
Greg S.
----------------------------------------
> To: [email protected]; [email protected]
> Subject: Re: [meteorite-list] Crystals in Lunar Meteorites...?
> Date: Wed, 29 Dec 2010 18:51:46 -0500
> From: [email protected]
>
>
> Hi Greg, Randy, List,
>
> I have been wondering the same thing since I've recently cut a few of
> my lunar suspects recently. To put Greg's question a little different,
> do lunar meteorites ever have crystaline shapes? Can you see with the
> naked eye or a loupe actual crystal structures like 6 sided or 8 sided
> crystals?
>
> Sincerely,
> Larry Atkins
> IMCA # 1941
> Ebay username alienrockfarm
> www.poisonivycontrolofmichigan.com
>
>
> -----Original Message-----
> From: Thunder Stone
> To: [email protected]; [email protected]
> Sent: Wed, Dec 29, 2010 11:55 am
> Subject: Re: [meteorite-list] Crystals in Lunar Meteorites...?
>
>
> Thanks Randy:It does to some degree and thanks for the links.I keep
> reading that lunar rocks contain "clasts," which I interpret as a
> grouping of crystals mashed together from a previous rock, and not
> individual crystals. I also read "grains" too.Let me put it another
> way: Do lunar rocks ever contain large crystals of feldspar or pyroxene
> like you may see in granite or a pegmetite? I unfortunately only have
> one very small lunar and have only seen others briefly.I'm convinced if
> a lunar has lost its fusion crust - it would be very difficult to
> identify when found.Greg S.---------------------------------------->
> Date: Wed, 29 Dec 2010 13:05:38 -0600> To:
> [email protected]> From: [email protected]> Subject:
> Re: [meteorite-list] Crystals in Lunar Meteorites...?>> Greg:>> All
> lunar meteorites contain mineral crystals. The basalts (both> breccias
> and unbrecciated) are composed mainly of crystals of> pyroxene and
> plagioclase feldspar. Some contain olivine, and all> contain minor
> ilmenite and related iron-titanium minerals. The> feldspathic breccias
> are largely crystalline. The only> noncrystalline material is glass and
> a little metal. "Crushed rock"> is crushed crystalline material. In
> some lunar meteorites the> plagioclase has been shock converted to
> maskelynite which,> technically, isn't a crystal but more like glass.>>
> Put another way, in photomicrographs of lunar meteorites (or any> rock)
> under "cross-polarized light" (NOT "plane polarized light") or>
> "crossed nichols," any and all non-black material is crystalline.>>
> There are some here:>>
> http://curator.jsc.nasa.gov/antmet/PDFFiles/B07_LAP02205v3.pdf < basalt
> >> http://curator.jsc.nasa.gov/antmet/PDFFiles/F23_GRA06157v3.pdf <>
> feldspathic breccia >>
> http://curator.jsc.nasa.gov/antmet/PDFFiles/F24_LAR06638v3.pdf <>
> feldspathic breccia >>
> http://curator.jsc.nasa.gov/antmet/PDFFiles/M07_MET01210v3.pdf <>
> basaltic breccia >>> Does this answer your question?>> Randy
> Korotev>>>>>>> At 11:59 AM 2010-12-29 Wednesday, you wrote:>> >List:>
> >> >I hope everyone had a prosperous and joyful Holiday Season.> >> >I
> was wondering something:> >> >Do lunar meteorites ever contain
> crystals? Or are the just crushed> >rock and lunar soil compacted
> together? From what I've been able to> >find is that any basalt type
> rock containing white feldspar that are> >crystals or if there is
> opaque crystals (ilmenite or> >magnetite...etc.), then it cannot be
> lunar, is this true? Are there> >some cases where you could find
> crystals within a lunar rock?> >> >Much Thanks and everyone have a
> happy New Year.> >> >Greg S.> >>
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