The petrographical microscope

What is this kind of microscope?
The petrographical microscope is an instrument used to observe minerals and rocks using magnifications up to 400 x.
Are all the petrographical microscopes identical?
There are two main types of microscopes: those using transmitted light and those that uses reflected light (in some models is possible to have the two possibilities in the same apparatus). The transmitted light microscopes, the light source is located under the stage and the light is conducted by several lenses and passes throughout the thin section. The rock samples should be almost transparent in order to be crossed by the light. The microscopes using reflected light the source light is located above the stage and what is observed is the result of the minerals reflecting light. The opaque minerals are observed using this kind of microscope.

What are the particularity of these microscopes?
The petrographical microscopes distinguishes from the biological microscope in two main aspects:

The rotating stage is necessary to observe the characteristics of the minerals in all the directions.

What can be observed with the petrographical microscope?
Small details not seen on hand specimens like small minerals, their habit and structure. It is also possible to estimate the proportion of the different minerals.

Are all the rocks suitable for microscopical observations?
The thin sections should be transparent to be observed under transmitted light. This thin section should have not more than 0.03mm thick.