[meteorite-list] Point of Diminishing returns (Slice thickness)?

From: Steve Schoner <schoner_at_meteoritecentral.com>
Date: Tue, 8 Mar 2011 05:40:14 GMT
Message-ID: <20110307.224014.15847.0_at_webmail21.dca.untd.com>

Richard,

In my estimation in making petrographic thin sections, slices that are ultra thin are very difficult to carry on to a true thin section, which is very useful in petrographic studies.

I have done it but it requires many extra steps to prepare thin sections from ultra paper thin slices.

I would say that a slice with a thickness of .025" is about the lowest limit that I can effectively work with. And such thin slices would have to have maximum dimensions of no more than .5" in extent by .025" in thickness.

But it is possible to make thin sections of slices that are smaller than .5" in maximum dimensions if the thickness is less than .025"

The problem with larger paper thin slices is that one has to make one side absolutely flat to make a good petrographic thin section. This becomes ever more difficult as the maximum dimension of the slice increases due to what I call "potato chip" wavy surfaces. Not easy to work with.

Another problem with ultra thin pieces is that the pitting is often so great that the absolutely flat side makes the piece even thinner. And the finished slide often will have holes in it.

Paper thin slices in making thin sections also produces micro-fractures in the minerals due to the cutting process. And the depth of polishing may not remove these fractures.

So for the most part paper thin slices are usually refused by most thin section makers due to these problems.

Most require part slices no thinner than .1"

Steve Schoner
http://www.petroslides.com
IMCA Founding Member Emeritus




Message: 2
Date: Mon, 7 Mar 2011 15:08:41 -0800 (PST)
From: Richard Kowalski <damoclid at yahoo.com>
Subject: [meteorite-list] Point of Diminishing returns (Slice
        thickness)?
To: meteorite list <meteorite-list at meteoritecentral.com>
Message-ID: <941935.83457.qm at web113612.mail.gq1.yahoo.com>
Content-Type: text/plain; charset=us-ascii

These discussions about aesthetics of specimens vs their weight is rather interesting,
but it seems the lines of the subject are a bit blurred.

It seems the subject has come to comparing fragments to slices. I'm not sure this is a
fair comparison, but I understand it.

I am wondering what others think represents a point of diminishing returns in making a
slice paper thin. IOW at what point does cutting losses become too great to make the
aesthetic function of the prep & price excessive?

I guess I don't understand the desire for some ultra-thin prepped specimens. For example,
if a ultra-thin 1mm thick slice is being sold for the equivalent $80 per gram, and a
slice of the exact same material, the exact same size, but 4 times the weight (4mm thick)
is being offered at the exact same price, I'd be inclined to purchase the latter.

I understand the appeal of of thinner specimens and of course you can polish a slice so
finely it becomes a thin section, but is there some point where the prep becomes so
costly that is is in fact "too thin" for the buyer?

Thanks

--
Richard Kowalski
Full Moon Photography
IMCA #1081
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Received on Tue 08 Mar 2011 12:40:14 AM PST