An Article In Meteorite-Times Magazine
by Tom Phillips
The Right Microscope for You?
I have been asked many questions such as "what can be expected from this microscope" and I have talked to people who were disappointed when it became apparent that the microscope they bought will not do what they bought it for.
I do not recommend any brand. There are just to many good ones. What really maters is selecting the type of microscope for the job you want to do. I have tried to include all the types you are likely to encounter. I do not go into SEM's, microprobes, etc. because I don't know much and it is not likely you will accidentally bring home a SEM with a 800Kv power supply.
I must admit, I use aus Jena equipment. This is for the sole reason that research grade scopes are often sold very inexpensively, which can not be said for aus Jena's West German cousin, Zeiss. That's not to say I don't admire Zeiss, Nikon, Olympus, Leitz and on and on. I think my dream (thin section) scope would be a fully equipped Zeiss Ultraphot III.
This photo (the big one on the left) is an aus Jena Neophot 21. This is an inverted incident light microscope. What that means is you put polished samples face down on the stage. This is my first love in meteorite examination. Not just because no thin section is needed but because it lets you see what the material really looks like up close. The range of magnification is from 10X to 2000X
This micrograph was taken on the Neophot at a magnification of 345X. It is SaU 001. What a cool chondrule. It looks like a planet!
JaH 055 at 700X. Can you believe what is in some meteorites?
Axtell TX CV3
NWA 3157 C3
These two micrographs were an example of a thin section placed on the Neophot. Both were taken at a magnification of 345X.
The transmitted light microscope. This is the type that will give you the cool thin section colors when it is equipped with cross polarized light. This particular model, the aus Jena Fluoval, has both transmitted and incident light capacity.
Dho 850 LL3.4 3.5 160X
Juvinas Eucrite 400X
Mount Tazerait L5 760X
All 4 micrographs were taken in cross polarized light at various levels of magnification.
DAG 478 (L6) XE 160X
Juvinas Eucrite XE 160X
These shots are tricky! It is combined reflected (incident) and pass through (transmitted) cross polarized light. One method can easily drown out the other. These images show the color with the details of the opaque material still visible.
A basic starter microscope. The Stereo scope. I personally think it is the type that all meteorite collectors should start with. It is useful to examine unprepared samples. This particular microscope is an AO and I paid $15 for it at a swap meet. These are generally not very expensive and when combined with cross polarized light, can be very useful in working with meteorites.
This is an example of an image taken at a magnification of 15X with bright field light.
This is the same sample (not moved) with the addition of cross polarized light. It is like X-ray vision!
A polished meteorite slice viewed at 15 X.
Just for fun! My new toy. It is an aus Jena Interphako. Built on the Amplival infinity frame system that was introduced in 1968. This line of scopes was selected by NASA for examination of the first Lunar samples. A big deal, considering this is an East German company and that was cold war times.
This particular model is DIC (Differential Interference Contrast). Light is separated by a prism, passed through/reflected from the sample and then recombined. It is said that this scope can measure +/- 1 nm or 1/500 of a wave length of visible light! For when you really want to know just how big those Lunar features are.
Ideally, This scope is designed for measurement and the image is more like a grid of light and dark where light waves interfere. This example is just reflected DIC. No measurement functions are engaged. The images are like a 3 D map of the surface height. I have found however, the differences in reflectance, particularly in the more transparent material, will produce some stunning images.
Iron fleck at 700X viewed in cross polarized light.
The same fleck viewed in DIC.
This image taken at a magnification of 345X in DIC shows the effect of this process on semi transparent materials in meteorites. It looks like waves on a lake.
Dark field. You may see the description bright field or dark field. This is an example of bug parts taken in dark field. The light is directed at the object from the sides leaving the object well illuminated and the back ground black. In standard bright field the fine details would not be visible due to the bright white back ground. It really makes objects like these bug parts stand out but I have not found a use for this method in meteorite examination.
There is no way to make one microscope good in all methods but that is cool because we all have a valid excuse to give to our spouse as to why we NEED a new scope.
Tom Phillips can be reached by email at:/font>
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