[meteorite-list] Thin section not so thin...

From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Sun, 30 Oct 2011 20:59:27 -0400 (EDT)
Message-ID: <8CE657F792DA6E5-1298-106655_at_webmail-m161.sysops.aol.com>

PS---

Looks like Richard Hill has all the answers you asked:

http://www.lpl.arizona.edu/~rhill/fossil/thnsect.html

kindest wishes
Doug


-----Original Message-----
From: MexicoDoug <mexicodoug at aim.com>
To: dallepuz <dallepuz at telefonica.net>; Meteorite-list
<Meteorite-list at meteoritecentral.com>
Sent: Sun, Oct 30, 2011 7:52 pm
Subject: Re: [meteorite-list] Thin section not so thin...


"think the best way is to do it the same way as I did when I grind my
telescope mirror, using a second glass as a grinding tool Any
suggestions?"

Hola David

I've never ground a meteorite TS myself, but a while back I was in our
local geology department watching the technicans make a bunch of them.
It was basically on a massive slow rotating flat lap that had a huge
motor and the plate might as well be glass I suppose though you've got
to wonder if it will wear evenly which must be the trick to finishing
off a decent thin section. Anyway, like telescope grinding it takes a
long time but unlike telescope grinding there is no naturally
corrective spherical effect to save you to get your first approximated
curve (or in this case flat). He just took the appropriate grits and
he did nice figure eights if recall with the wrist, and invited me to
participate. But it got boring pretty quickly so the memory is foggy
;-)

Atentos saludos and say hi to Esmeralda for me!
(you're one of the three Iberian Cazameteorito buddies - aren't you?)

Kindest wishes
Doug



-----Original Message-----
From: dean bessey <deanbessey at yahoo.com>
To: meteorite-list <meteorite-list at meteoritecentral.com>
Sent: Sun, Oct 30, 2011 6:05 pm
Subject: Re: [meteorite-list] Thin section not so thin...


As a ebay seller of thin sections I thought that I would respond to
this. I
should point out that it wasnt me that David bought his thin section
from, I
dont know who he bought them from, dont know anything about his thin
section and
am in no way commenting on any other seller when I write this.
It should be pointed out that in order to be a "Thin Section" it does
not have
to be 30 microns. Thin Sections are extensively used by various
scientific and
commercial organizations for various purposes and in particular mining
and
petroleum companies make great use of thin sections.
Depending on what you are trying to do different thickness's might be
most
useful. For meteorite classification purposes it must be 30 microns as
the light
will be different from what it is supposed to be if it is some other
thickness
(All of my own thin sections are 30 microns). There are other standard
thicknesses and 100 microns I believe is the most common (And possibly
cheapest
to make). 50 and 200 micron thickness thin sections are also standard
thicknesses (But meteorite people rarely would want one this thickness).
We on this list are most familiar with 30 microns because thats the
thickness
thats needed for meteorite classifications. If you were working as a
geologists
with a petroleum company you might be more familiar with 100 micron
thin
sections.
I suspect that the thin section David bought was made to a different
standard
than for what you usually need for meteorites. It would be odd to be
exactly
another standard thickness if it was just a poor job. (For example if
it was say
85 microns I would probably say that it was a poor job as probably
nobody would
ever make a thin section that thickness no matter what the planned use
was)
I would also like to comment on the price of thin sections. You will
notice that
my meteorite thin sections are priced cheaper than most other sellers
(Started
on ebay as low as $29.95). When I left Canada 7 years ago I left a
container of
stuff in storage which I only got earlier this year. Since it was all
paid for
more than half a decade ago I am selling off a lot of it with no regard
to my
cost or replacement value. My thin sections fall in this catagory. I
cant
replace thin sections and make money at $29.95.
I will not get into a slugging match by saying mine are better than
other people
and you should pay more for mine because of that but if you do see thin
sections
cheaper than what I currently have listed I would be suspicion and ask
questions
before I buy. Its possible that somebody in a country where labour is
cheaper
can make them cheaper than me (Although I would love to know if anybody
does
find a place)
Questions that you should ask are:
(1) Thickness. Are they 30 micrions, 100 micron or some other thickness
(I am
assuming that the seller would know this)
(2) Are they Polished? Unpolished thin setions can easily be made for
under $20.
It costs as much to polish them as it does to cut them. Both have their
uses but
polished ones are twice as expensive (And needed if you want to get the
meteorite classified).
(3) Do they have a cover slip? If you will carbon coat them and put
them in a
microprobe (Needed if you buy one of my "Thin scetion kits" on ebay and
send it
for classification) you DO NOT want a cover slip. If you are just using
them
with a standard microscope and showing them in schools you might want
the cover
slip so it wont get scratched.
Hope this helps somebody
Sincerely
DEAN (AMUNRE on ebay)
http://stores.ebay.com/The-AmunRe-Museum/_i.html?_nkw=thin+section&submit=Search&_sid=1598024










--- On Sun, 30/10/11, David Allepuz <dallepuz at telefonica.net> wrote:

> From: David Allepuz <dallepuz at telefonica.net>
> Subject: [meteorite-list] Thin section not so thin...
> To: meteorite-list at meteoritecentral.com
> Received: Sunday, 30 October, 2011, 12:46 PM
>
> Hello list,
>
> A few weeks ago I bought a NWA869 thin section from an eBay
> seller.
>
> The seller is not Mirko Graul (excellent thin section
> seller, excellent person, my favorite? thin section
> provider) nor any known thin section seller of this list, OK
> ?
>
>
> When received it looked darker than usual and after
> measuring thickness it was 100 micrometers instead of 30.
> I just contacted the seller to prevent it from selling more
> thin sections like this and having problems with costumers,
> but in a educational and collaborative way, as I think he
> was new in thin sections and did not know about the
> problem.
> The thin section was really cheap, so I keep it, no
> problem.
>
> Ok, well, my help claim is because I want to grind that
> thin section to 30 micrometers and I think the best way is
> to do it the same way as I did when I grind my telescope
> mirror, using a second glass as a grinding tool.
> Any suggestions?
> Do I use carborundum 2000 or Aluminium Oxide?
>
> Thank you.
>
>
> David Allepuz
> Corbera de Llobregat
> Catalonia -SPAIN
>
> www.meteorits.cat
> www.cazameteoritos.es
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Received on Sun 30 Oct 2011 08:59:27 PM PDT