As with any other instrument, proper use will determine if you get accurate results. The stone is held close to the aperture, even slightly touching it, with a strong allochromatic, white light source behind the stone. When one looks through the other end of the dichroscope, two small windows next to each other will be seen with a color in each of the windows. These colors may either be the same or different colors or different shades of colors. Now turn the dichroscope slowly 180° between your fingers while keeping the stone in a fixed position and observe if the colors in the two windows are the same or if they differ.