[meteorite-list] Mohs hardness and meteorites

From: Galactic Stone & Ironworks <meteoritemike_at_meteoritecentral.com>
Date: Sat, 14 May 2011 09:29:19 -0400
Message-ID: <BANLkTi=spNii_uJ_K=GmxJs-d_Y2HgNtTw_at_mail.gmail.com>

Hi Folks,

Thanks for the helpful replies. :)

While meteorites are a heterogeneous mixture of minerals that have
varying individual hardnesses, taken as a sum of the parts, it seems
that some meteorites are definitely harder than others. This also
seems to apply to some meteorites within the same petrologic type.

Thinking back on some of the different types I have cut, here is a
rough scale of hardness for meteorites I have encountered -

10 - Whitecourt iron (ruined my blade)

9 - NWA 788 (this was like cutting the hardest stone possible - like
Dwarven adamantine. I was very surprised at how tough this stone was.
 It was very time-consuming to polish also.)

8 - NWA 6386 - this diogenite is very compact and glassy. It's like
cutting a tektite, but tougher. (this includes NWA 6288 and another
possible pairing)

7 - Toufassour - or any similar mesosiderite. Difficulty is related
to overall metal content of the individual specimen. (some are tougher
than others)

6 - an old NWA CV3. I forget the number, but it was very tough and
slow to cut.

5 - most NWA ordinary chondrites - tough, but a fresh blade makes
quick work of them.

4 - most LL type chondrites (and highly weathered chondrites like Al-Haggounia)

3 - Allende, NWA 6026 (CK5), and most howardites/eucrites.

2 - anything this soft I usually dry-cut.


Best regards,

MikeG

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On 5/14/11, Jimski47 at aol.com <Jimski47 at aol.com> wrote:
>
>
> In a message dated 5/9/2011 4:24:28 P.M. Central Daylight Time,
> meteoritemike at gmail.com writes:
> Hi List,
>
> Has anyone ever put together a hardness list for meteorites in
> relation to the Mohs scale?
>
> I know that irons, stony-irons, friable types (some achondrites, LL's)
> will vary greatly in hardness. But what I am curious about is stony
> type meteorites, specifically the chondrite family. For example,
> let's take the "typical" H5 chondrite - one of the most common of all
> meteorite types. Where does the H5 fall on the Mohs hardness scale?
>
> Up until the time I started cutting and polishing meteorites, I
> assumed that an L5 would be "softer" than an H5. But, I have run
> across some L-chondrites that are very very hard and require the same
> amount of sanding/polishing work as some H-chondrites. I am assuming
> this is because of the individual mineral compositions of the
> meteorites in questions, and not so much the petrologic type. So am I
> right to assume that stony meteorite hardness is not dictated solely
> by iron content?
>
> Best regards,
>
> Mike Gilmer
> --
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> Galactic Stone & Ironworks - Meteorites & Amber
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>
> Hi Mike,
>
> Yes I believe your right to assume that iron content of a chondrite does
> not dictate it's hardness. An iron meteorite has a hardness of 4-5 which is
> what you would get if the test point of the chondrite was on a iron flake.
> It could be higher if the test point was in the matrix and that would
> depend
> on the composition of the matrix. Feldspar which has been found in
> meteorites has a hardness of 6 and diamond is a 10.
>
> Jim Konwerski
>
>

--

Received on Sat 14 May 2011 09:29:19 AM PDT