Pleochroism Light that passes through a doubly refractive gemstone or anisotropic mineral is split in different directions with varying velocity. The light is absorbed differently in different vibration directions, resulting in color variation known as pleochroism . In minerals with only two rays, two pleochroic colors can be detected, called dichroism. Pleochroism can be detected with the polariscope, although the calcite dichroscope is the preferred gem instrument to view pleochroism. The dichroscope is a metal tube with a opening at one end and lens at the other.
Optical calcite is mounted inside the tube, producing a double image of the square opening.
When the gem is held over a bright light source and viewed through the dichroscope, each image has a different color indicating the vibration directions are at right angles and vary in wavelength. When two differing colors are detected, confirm pleochroism by rotating the instrument 90 degrees and the two colors should switch sides on the split image. Trichroism can be detected by changing the orientation of the stone and one new color will be detected alongside one of the colors seen in the other orientation. An ESU student. The function of magnification, whether by a hand held lens or the microscope, is to enlarge an image of the object so details become clear on both the surface and interior.