[meteorite-list] Polishing Question???

From: tett <tett_at_meteoritecentral.com>
Date: Thu Apr 22 09:48:12 2004
Message-ID: <3BD00B23.B59322C9_at_bmts.com>

David,

I have polished lots of slices and it is a simple matter of carefully using silcon-carbide paper in increasing grit increments.

If you get a slice with deep saw marks then you will have to start with as low as 120 grit. Most slice are small enough that you can polish
all by hand. Working on a piece of glass polish the slice until the piece is nice and flat. Work up to about 400 grit. You can use alcohol
with the paper to help the process. At 400 grit most chondrites show there best. You do not have to go higher and if you do many chondrites
will actually lose definition. There are some exceptions, however. I just polished an LL3 to 1200 grit and it looks incredible. If you go to
higher grits then the finishing passes should be very gentle and done in a figure 8 pattern to get a nice polish. After each increment wash in
alcohol and let dry before deciding if you want to go higher.

With all that said, some chondrites look best direct from the saw cut. Slices from people that know what they are doing should be smooth and
actually close to a 400 grit finish already.

Experimentation is the key.

I am also an advocate of cleaning some chondrites with Navel Jelly. I do this to ones that show rust stains. With some, the chondrules just
jump out after being soaked in navel jelly after an hour. My best results were with slices of Juancheng, Selma, and Zag. The difference is
incredible. I am sure many would cringe at the thought of soaking a meteorite in such strong acid and I have been warned by experts that I
should be prepared to "lose a few". So far so good. I have many slices which I have soaked in Navel Jelly that are still stable after a few
years and I have had no ruined slices.

Very Important! If you are going to try Navel Jelly then take all the precautions one must take when using strong acids. As well, be warned
that Navel Jelly stinks. Prepare the slice and soak for 1 hour. Wash in clean water and view your result. If still lots of stains then soak
for longer. I have soaked a slice over night. The first hour does most of the cleaning and any longer only helps to a very small degree.
Once finished, then soak the slice for a few days in alcohol. You may even want to change the alcohol once during the final soak. This soak
is critical to remove any water from the rinsing and to remove any acid.

Any dark crust may come out chalky after this acid process. I have used mineral oil on the crust to clean this of.

Again, experimentation is the key and remember "be prepared to lose a few".

Cheers,

tett
aka Mike Tettenborn

Dave Schultz wrote:

> Greetings Listees. I know this question has probably been hashed over many
> times, but I would like to know again what the steps are to really bring out
> the brecciation and chondrules in meteorite slices, or maybe even a link to
> help me. I`ve seen some cool looking pictures of slices lately with these
> features really standing out. Sorry if I`m being redundant! Dave
>
> Show your support at the Red Cross Disaster Relief Fund - http://s1.amazon.com/exec/varzea/ts/my-pay-page/PKAXFNQH7EKCX/058-5084202-7156648
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Received on Fri 19 Oct 2001 07:14:43 AM PDT