[meteorite-list] need info composition of lunar meteorites

From: Norbert Classen <trifid_at_meteoritecentral.com>
Date: Thu, 7 Jun 2007 22:57:58 +0200
Message-ID: <001801c7a946$89d9ddb0$2002a8c0_at_lunatic>

Hi Dan,

I'm pretty sure that he meant anorthite (the mineral), and not anorthosite
(the rock type) - it's easy to confuse the two, especially if you consider
that most list members or hobby meteorite enthusiasts are no mineralogists,
or petrologists.

That being said, anorthosite was certainly not found in all rocks returned
from the Moon, but if you say "anorthitic placioclase" that would make
perfect sense, even for the lunar mare basalts. It would also make sense to
say that most of the ancient lunar crust (the lunar highlands) is composed
primarily of anorthositic rocks and breccias - many meteoriticists use the
term "anorthositic" but also the term "feldspatic" when it comes to the
classification of lunar rocks as you will see if you study Randy Korotev's
great site about lunar meteorites (the best one around):


To quote Randy Korotev: "Lunar rocks are classified by what minerals they
contain (mineralogy), how the mineral grains are put together (texture), how
the rock formed (petrology), and chemical composition (chemistry). These
different parameters sometimes leads to confusion because a geochemist might
call a rock ?feldspathic? (dominant mineral) or ?aluminum rich,? (chemical
composition) while a petrologist might call it an ?anorthosite? (mineral
proportions and implied mode of formation) or ?regolith breccia? (texture
and and type of rock components)."

He also notes that not all petrologists (not to speak of mineralogists ,-)
do always easily agree on the classification on any given lunar rock (and
that's an understatement, IMHO). What I'm trying to say is that it's very
easy to make a small mistake in wording when it comes to this particular
field when even the scientists do not always agree on how to call a given
rock, and when he's used to hear terms like "anorthosite-bearing basaltic
regolith breccia" and the like which are commonly used when it comes to the
classification of lunar meteorites.

Hope this helps?

Best Regards from Germany,
Norbert Classen
Planetary Meteorites

PS: I'm no mineralogist/petrologist, but merely an educated layman, and it
just happens that lunar meteorites are my favourite obsession...

-----Urspr?ngliche Nachricht-----


I joined this list at the behest of someone from the
IMCA based on concerns I have with something being
advertised as a meteorite. Among other errors and
misstatements, the ad states that "Anorthosite was
found in all the rocks returned from the Moon..." As
a mineralogist I find this difficult to believe.
Anorthosite is defined as a rock type that contains
>90% feldspar and is off-white in color, with perhaps
a few inclusions of other minerals. On the other
hand, anorthite (note the subtle difference in
spelling) is a mineral species consisting of anorthite
feldspar, the calcic end member of the plagioclase
series. To make things more confusing, anorthite
occurs as a component of anorthosite, but the two
words mean quite different things.

I sent two e-mails to the seller via eBay, and have
received no response. I would have liked to think the
seller simply made some mistakes and listed a common
terrestrial rock as a meteorite, but the lack of
response gives me doubt. However, I am also curious
about where he might have obtained the statement with
which I opened this note, as far as whether the
original publication indeed says "anorthite" and that
is simply a mistype on his part.

Received on Thu 07 Jun 2007 04:57:58 PM PDT

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