Eduardo M. Libby
Humans have been obsessed with jewels and precious metals for thousands of years. (We seem to really like shiny objects, unlike crows.) We’ve gotten good at mimicking gems like diamonds and rubies in glass and crystal, and metallic paints look nearly realistic these days. But nature has long had us beat — if you know where to look, you can find living plants and animals that appear to have been made of gold or silver or gems. Here are a few of my favorites:
Gold and silver beetles
Costa Rica is home to two species of beetles that are certain to turn heads: Chrysina aurigans, which looks like it’s made of solid gold, and C. limbata, a related species that’s solid silver. The beetles’ forewings are covered in 70 layers of chitin, and each of these layers reflects a bit of light. That light all adds up to a brilliant shine, researchers reported in 2011 in Optical Materials Express.
When a male splendid sunbird of west Africa sits out in the sun, it looks like he is bathing in microscopic jewels. While this bird may be particularly impressive in its iridescence, this is a quality that’s actually fairly common in the bird world (and it’s been around for at least 40 million years, Science News reported in 2009). The iridescent trait probably arose several times in evolution, researchers noted in a review of iridescence in the animal world published in Interface in 2009. “In birds,” they wrote, “the nanostructural organization of keratin, melanin and air in feather barbules can produce iridescent coloration through thin films, multilayer reflectors or photonic crystals.” There’s lots of ways to get a jewel-colored bird, it seems.
Male Sapphirina appear to glow because light is reflected off the layers of crystal plates that cover their bodies.liquidguru/Vimeo
Male copepods of the genus Sapphirina appear to shine, taking on colors such as sapphire blue, golden green and splendid purple. The tiny marine creatures don’t produce their own light — it just appears that they do because of the way light is reflected off the layers of crystal plates that cover the copepod.
“In the case of blue sea sapphires, these crystal layers are separated by only about four ten-thousandths of a millimeter; about the same distance as a wavelength of blue light,” Rebecca Helm wrote last month at Deep Sea News. “When blue light bounces off these crystal layers, it is perfectly preserved and reflected.” You can see that in the video at the right.
The fruit of the Pollia condensataplant of Africa shines a brilliant blue that is more instense than that found in any other biological material. There is no actual blue coloring in the berry, however. The fruits are covered with layers of nanoscale-sized strands of cellulose. Light reflects off those layers and produces a color. But that color varies from cell to cell because the distance between the layers varies. One cell may produce a red color, another green, but the overall effect is the otherworldly blue that persists even on fruits long preserved in an herbarium, researchers reported in the Proceedings of the National Academy of Sciences in 2012.