[meteorite-list] what is the world standards for petrographical preparations(polarization microscopy)

From: Paul H <bristolia_at_meteoritecentral.com>
Date: Thu May 27 20:56:24 2004
Message-ID: <20040528004416.9273.qmail_at_web50805.mail.yahoo.com>

E. L. Jones jonee at epix.net wrote:

>I am also interested in the use of "quartz"
>as index markers. This isn't in any of my
>reference books. Are they attached to the
>specimen and ground at the same time as the
>thin section?

No. The person grinding the thin section uses
the bifringence of whatever minerals are
present to judge the thickness of the thin
section. Quartz is used as an index marker
simply because, it is so common as to be
present in most sedimentary, igneous, and
metamorphic rocks. When it isn't present,
a person uses whatever mineral happens to
be in the thin section as an index.

Some web pages are:

Making Petrographic Thin Sections
http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/thinsections.htm
http://almandine.geol.wwu.edu/~dave/other/thinsections/
http://www.lpl.arizona.edu/~rhill/fossil/thnsect.html

Making Petrographic Thin Sections
http://www.uni-wuerzburg.de/mineralogie/links/tools/making.html

Rock-Forming Minerals in Thin Section
http://www.uwgb.edu/dutchs/petrolgy/thinsect.htm

Atlas of Rocks and Minerals Under the Microscope
http://www.geologynet.com/thins.htm

Igneous rocks in thin section
http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/ig_minerals.htm

Minerals in thin sections
http://www.uni-wuerzburg.de/mineralogie/links/petrology/thinsection.html

>Another question I have. Is there a house
>that specializes in preparation? Kinda of
>like the $2 a carat faceting deals one can
>get in Thailand?
 
There are many places that specialize in making
thin sections. Typically, a person gets what
they pay for. A quick search using Google will
find a number petrographic labs that make thin
sections. If you are going to pay 5 to 50 dollars
a gram for a meteorite, paying 15.00 dollars for
a high quality thin section is the least of
your costs.

The people that use to make the thin sections for
my research (and search for more shocked quartz)
from samples in the Brushy Creek Carter is:

National Petrographic Service, Inc.
5933 Bellaire Blvd., Suite 108
Houston, TX 77081
http://www.nationalpetrographic.com/

Their price list is at:
http://www.nationalpetrographic.com/thin_sections.htm

Their price are average for what thin sections cost.

Elton

>Roman Davidov wrote:
>>Dear list members. Hello.
>>My question is: What is the world standards for
>>petrographical preparations. If I'm not mistaken
>>in English it sounds like "THIN SECTIONS".

Yes, as noted above, the term is "thin section".

>To be more concrete I mean: form and sizes of
>object glass (width,height,thickness);

The glass slide of the standard thin section is
27 x 46mm (1" x 1 7/8"). Larger slides are produced,
but size might vary according to the lab that
prepares them. For example, National Petrographic
has 38 x 75mm (1.5" x 3") and 50 x 75mm (2" x 3")
size glass slides for larger size thin sections.

>type of optical glue (we are using composition
>named "Canadian Balsam");

Hillquist A-B is used to glue slabs to slides.
However, Canadium Balsam is the standard for
attaching the coverslip. If you want to do any
microprobe, etxching, or similar work, i.e. for
identifying shocked quartz, the thin section needs
to be finished by polishing and the coverslip
left off.

>linear sizes of object (I'm sure that thickness
>is one to all of the world - 0.003 millimeters);
>form and sizes of cover glass.

The only requirement for the size of the object
is that it is a few mm smaller than the size of
the glass slide being used. The coverslip is
larger than the specimen and smaller than
the slide.

The coverslips come in sizes, thicknesses, and
optical character that are standardized for use
in making thin sections. A person needs to talk
with the people supplying the coverslips and
get the technical specifications of what they
are selling to see if they are suitable for
thin sections.

...text deleted...

Yours,

Paul
Baton Rouge, LA





        
                
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Received on Thu 27 May 2004 08:44:16 PM PDT