Iolite (Cordierite) is pleochroic. Meaning the color changes depending on the direction in which light is passed through the stone. Most typically from blue to yellow.
This quality would be great for cabochons or tumbling.
Photos have not been edited or altered, just taken in different daylight conditions to show the variation in color. Pieces are held in hand to help with scale and does not necessarily represent 100 grams. Specific pieces photographed may no longer be available.