Photomicrographs were taken with a camera (the most recent images with a digital reflex) mounted on an optical microscope using transmitted polarized light, generally with crossed polarizers.
In order to be transparent, the rock is cut, sliced, thinned down to 30-micron (0.03 mm) thickness and mounted on a glass holder: such “thin section” is the ordinary research tool of a geologist.
The technique doesn’t include any manipulation during or after shooting: the variety and tones of interference colors are the results of the natural propagation of polarized light into minerals, and of the use of the accessory “λ“ compensator.
Except for single crystals (e.g. Gypsum), or plastic fragments, all the subjects are thin sections of rocks of metamorphic or magmatic origin.
The size of subjects (width of view) varies in the range 0.2 - 5.0mm, corresponding to 2,5X to 20X lens magnification.