Views of a “Chondritic Meteorite” in thin section. This is a meteorite that was polished to only about 0.03 millimeters thick, thin enough that light can travel
through the rocks. It is then put on a polarizing microscope and polarized light is sent through it. That gives you a chance to see some of the minerals and textures,
but there is a second step here. A geologists microscope will have a second polarizer above the sample. That second polarizer can be rotated so that only light that
had its direction changed by passing through the mineral reaches the eye of the viewer. This produces an effect called Birefringence, the colors seen in these grains.
Birefringence colors can be used along with mineral textures to identify rock types.
This video shows the upper polarizer being rotated, so the light goes from singly-polarized to doubly polarized and colors appear as they do it. The spherical blobs
in this sample are the chondrules. They are thought to have been blobs of rapidly melted, rapidly cooled rock that floated out in space. Eventually they were assembled
into rocks on some of the early asteroids.
Chondrules in cross polarized light
https://vimeo.com/103549466