I have written about color change in tourmaline a lot on my website because the discovery of Laurellite, a cuprian tourmaline from Mozambique that has a reverse Alexandrite color change, is a principal reason for this site’s existence. The strong effect of different “white” lights on the dynamic colors of tourmaline is far from limited to color changers like Laurellite.
The “white” lights I am referring to in this post are artificial light and natural light. You will see that the interaction of these over-simplified sources of light can affect the visual appearance of tourmaline in other ways.
If you would ask me which color in tourmaline is my favorite, I would respond with vivid. Vivid is a common way to describe a color’s purity or level of saturation. Saturation, in this case, is not the level of darkness of the color, that is tone value. A subject for other posts. In this context, the commonly used phrase “The gem is overly saturated” does not make sense. You can not have a gem that is undesirable because its color is too pure. The broad and varied nature of “white” lights in the everyday world can strongly affect some gems more than others.
I find the effect of light on the vividness of tourmaline as a group to be much more complex than just declaring tourmaline a daytime or nighttime gemstone. (You would find your tourmalines to be most attractive during the day or night.) It also depends on the color of the tourmaline and in the following paragraphs, I will try and give you my observations about changes in vividness and the colors of tourmaline.
Let us start at the long-wavelength end of the spectrum that is red. The boundary between red and pink in tourmaline is ambiguous for a very good reason since both red and pink are different tone values of the same hue. The classic lament about red tourmaline is that some examples turn brownish in artificial light. This has gone to the point that some members of the trade will only use Rubellite, the classic name for red tourmaline, for gems that do not turn brownish. Most of my tourmaline rough comes from Africa and I have not seen this problem, desaturation, in this material, but I do have examples of reds that are permanently brown because of the mixed nature of their color. By mixed colors, I mean colors like gray, brown, and purple that are not hues found in the spectrum of white light. They have no place in color worlds and represent a diminished level of purity (vividness) in a gems hue not a change in hue.
Now that we have a red tourmaline with stable color, how does its vividness change between artificial light and natural light? Since artificial light is redder you would think that the gems would become significantly more vivid, but I see relatively little change in red/pinks. I certainly see them turn purplish, again a mixed color, in cooler natural lights. Just like brown tourmaline that are really desaturated red, there are many Rubellites that are permanently purplish.
Moving on to orange in tourmaline is to step into both a spectral hue and a mixed color (red and yellow) world. I have spent a significant amount of both time and resources tracking down this elusive color. I have had some success, but not really enough to determine that tourmaline with a pure hue increase their vividness more than moderately in artificial light. I do not see a significant change in pastel oranges that I usually call peach and the Dravite’s brownish-orange. I have been able to get spicy browns from East Africa that I like to put into a different category the traditional Dravites. I have come to call them names like mahogany and common spice names. They can be quite bright and be shown by observation and the spectrometer to be a mixed color based on orange.
Yellows in the tourmaline world always seem to walk on the edge of green or brown. Most purer yellow in my collection are pastel in tone and do respond to yellowish light by being moderately more vivid.in Still they never reach the level of saturation that is seen in vivid yellow tourmaline from East Africa that has come to be called canary. I don’t know how canary responds to change light since I have only seen it in pictures. Greenish-yellow is the most common variety of tourmaline that I put in the category of yellow. It can be a very flashy variety that is quite stable in vividness.
Tourmaline has a tremendous range of colors in the green range. Common olive green tourmaline is not very vivid and remains that way under any reasonable light. Chrome tourmaline can have varying amounts of brown in it depending on how blue the white light is, but a top-grade chrome is just plain vivid its whole life. Elbaite, lithia tourmaline, can be quite vivid too, but having two axes of color generally renders it a more complex picture than chrome. It also seems more responsive, in vividness to changing light. As tourmaline grades into blue, it loses its propensity to have a brownish overtone. Many tourmaline this color range excites me with their vividness while I am cutting them under incandescent light only to desaturate under the cold blueish light of the morning. Gray, a mixed color can certainly impact bluer greens and indicates desaturation.
Blue loves incandescent light period. It does not darken the stone, like some other blue gemstones. And if one of my dreams about vivid tourmaline would come true, it would be that some of my best blue tourmalines would remain as vivid under natural light as incandescent light. As is true with most colors of tourmaline, The best is great under any reasonable light. I say reasonable light, because too much yellow can adversely affect my beautiful blues.
Purple is a mixed color and a yellowish light plays with its soul. Color, tone and saturation are degraded in my opinion. Gray can become a big factor in purplish tourmaline and make its vividness quite stable, but not more attractive to me. Still, I find people who love a desaturated color in tourmaline, much to my surprise.
My mother use to say it is good to be moderate in all things. But I will never be moderate in my passion for vivid color in tourmaline. Every collector of tourmaline, worth their salt, should see their collection under both incandescent light and natural light. Even pastels will fire up under bright defused natural light, as the sun sets on this post.