Color Change Garnet
Structure : X3Y2(SiO4)3,Color change garnet is a type of garnet that exhibits different colors under different light sources. It is typically a hybrid-mix of spessartine and pyrope garnet and may also contain traces of grossularite or almandine garnet1. The chemical composition of color change garnet can vary depending on the proportions of these end members, but it generally has the formula X3Y2(SiO4)3, where X can be calcium or magnesium and Y can be aluminium, iron, chromium or manganese2. Some examples of color change garnet compositions are: A chromium-rich pyrope with more than 3 wt.% chromium that changes from green to bluish green in daylight to red to reddish purple in incandescent light3. A spessartine with 80.37 mol.% spessartine and minor contributions from other garnet species that changes from dark green in daylight to dark red in incandescent light4. A pyrope-spessartine with 29–46 mol.% spessartine that changes from blue-green to purple1. The color change phenomenon in garnet is caused by the selective absorption of different wavelengths of light by the garnet’s chemical composition. Depending on the light source, some colors are absorbed more than others, resulting in different perceived colors. For example, a chromium-rich pyrope garnet absorbs more blue and yellow light under daylight, making it appear green, but absorbs more green and blue light under incandescent light, making it appear red1. Similarly, a spessartine garnet absorbs more red and yellow light under daylight, making it appear dark green, but absorbs more green and blue light under incandescent light, making it appear dark red1. The color change can be quite dramatic and often surpasses that of alexandrite, a rare gemstone that is famous for its color change2.