On the ruler, the leftmost garnet is from Koherab, Namibia while the remaining garnets are from Garnet Ridge, Arizona. The four garnets on the left display thermochromism -changing to green when heated- while the rightmost garnets do not. The scale is centimeters.
These are the locations of the garnets:
The graph below represents absorption of visible light. The peaks where absoprtion are high indicate the wavelengths of light which are not transmitted by the sample. The low regions of the graph represent the wavelengths of color which aren't absorbed- meaning the composition of all these wavelenghts is the final color our eyes percieve. Also the human eye is most sensitive to light in the yellow region, which affects the percieved color versus the actual color.
This graph displays the relations between mixed colors and wavelengths.