In the early 1980s I was running the photo department at a scientific research establishment. This involved a wide variety photo techniques to record a range of subjects.
However, polarized light photomicroscopy wasn’t used for anything work related. Having seen the results of other people I decided to investigate the technique. In those days that meant researching in literature rather than simply Googling as you would these days.
Now I will admit that I am writing this from memory, I have googled the subject and what I have found matches my memories of the technique.
I applied drops of a Sodium Thiosulfate solution to some microscope slides and left the solution to evaporate so that crystals would form.
I mounted a polarizing filter between the light source of the microscope and the slide stage. Once the Sodium Thiosulfate had crystallized I put one of the microscope slides on the stage and put a second polarizing filter above the slide. When you rotated one of the polarizing filters the colour of the crystals changed.
The first photo shows what I found to be a fairly typical example of the crystals.
This photo shows small patches of colour against a mostly dark background. I’m guessing that this is a result of the orientation of the polarizing filters.