[meteorite-list] polarizers

[STARSANDSCOPES at aol.com]

In a message dated 9/23/2007 6:56:09 A.M.  Mountain Daylight Time, 
marcin at polandmet.com writes:
Hi Tom.
I just read  Your january article about polarizers.
But I dont understand how You can see  chondruls through surface ?
Your photos are incredible, but I can't imagine  how You do that without 
polishing surface to remove polished surface  (polished by sand).

When I look into stone through one polarizers nothing  happend, when I get 
two then nothing happend, only screen become darker when  I rotate it. So how 
did You do that :)

My polirize filters are nice  for most of TS, but maybe there are better ? 
Any suggestions  ?



Glad you asked!

Hi Marcin and list members,  If the  whole image is getting darker when the 
polarizers are rotated then they are not  positioned correctly.

Always remember:

One filter between the  light source and the sample.

One filter between the sample and the  microscope objective (or your eye if 
no microscope is used).

This concept  applies to both transmitted (pass through) and incident 
(reflected) light.   

Only transmitted Xpol produces the vivid colors associated with Xpol  
examination.  


In answer to Marcin's question.  Those rocks  were examined as shown in the 
first picture with no prep work.  The samples  were imaged as you see them!  
The results are so important in examining an  uncut sample, I don't understand 
why every one who collects meteorites does not  have a cross polarized light 
set up.

Marcin's other question about what  polarizers to use.  On my Neophot I use a 
Glan-Thompson style that produces  almost total extinction.  These polarizers 
are expensive and bulky, you  don't need those at nearly $500 each (and it's 
X2).  I don't however, like  the films.  The ones I have tried distort the 
viewing with an irregular  film surface.  Particularly avoid the adhesive backed 
films as they are the  worst for distortion,

I like glass camera filters.  What ever style  works fine.  Circular is my 
first pick.  These are cheap used almost  any where.  Even eBay can be a cheap 
source.  Quality glass camera  filters to not disrupt the image and the metal 
frame often allows for  rotation.  About half the filters I pick up rotate in 
their  holder.

Garage sales and thrift stores are my first hunting grounds and I  bought 
tons (translate: a lot!) at $1 or less.  Yep $1 was my cut  off.  Except for a 
huge 150mm monster I paid $5 for.  I haven't found  a use for it but I bought it 
because it was cool.

One further note.   If you have a rock saw, the class filters cut just fine.  
I have cut custom  sizes to fit inside microscopes and make for a near OEM 
application.

If  you are going to my Gallery, please look at the Juvinas Eucrite Xpol thin 
 section micrographs.  
http://www.meteorite.com/meteorite-gallery/Micro_Visions.htm

Jeff Hodges  owns the thin section.  It was polished to 1/4 micron on both 
sides.   This is a big deal as generally thin sections do not have a very high 
polish, as  it is not necessary to identify minerals and structure.   I am 
using  an aus Jena Aplanatic Pancratic Condenser.  This allows me to focus the  
incoming light exactly on the thin section and then focus the objective.   The 
results are stunning.

Please take a look and let me know what you  think.  You will be amazed.  
Don't just say you have seen plenty of  Xpol shots before "What makes Tom's so 
special?"  LOOK, it will be worth  your time.

Thanks,  Tom  




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