Purple is an enchanting color that has long been associated with royalty, spirituality, and mystery. Unlike other colors like green or brown, true purple pigments are rarely found in nature. This leads many to wonder – is anything naturally purple?
The Science of Purple
The color purple is a mix of red and blue light. On the color spectrum, it falls between the two, at around 450 nanometers wavelength. To create the perception of purple, an object must absorb green and yellow light, reflecting only red and blue wavelengths to our eyes.
In nature, most purple hues we see are created through a process called structural coloration. Rather than absorbing certain wavelengths, objects like peacock feathers, butterfly wings, and soap bubbles reflect light in a way that makes them appear iridescent purple and blue when viewed from certain angles.
True purple pigmentation, on the other hand, is much rarer. There are only a handful of naturally occurring molecular structures that selectively absorb green/yellow light. Finding these pigments in high enough concentrations to create a vivid purple color is unusual in the natural world.
Naturally Purple Plants
There are a few botanical exceptions to the scarcity of purple in nature. Several plant species have managed to evolve pigments that produce true purple hues in their flowers, fruits, leaves, and stems.
Purple Flowers
| Plant | Pigment |
|---|---|
| Lisianthius | Anthocyanin |
| Clematis | Anthocyanin |
| Iris | Anthocyanin |
| Hydrangea | Anthocyanin |
| Allium | Betacyanin |
| Rose | Delphinidin |
The most common purple flower pigments are anthocyanins and betacyanins. Anthocyanins also produce blue, red, and pink flower colors. They change color based on pH, taking on a more purple hue in neutral or acidic conditions.
Less common purple flower pigments include delphinidins like those found in purple roses, myrtles, and pansies. These molecules have a true violet color that does not change with pH.
Purple Fruits and Vegetables
| Food | Pigment |
|---|---|
| Eggplant | Anthocyanin |
| Purple corn | Anthocyanin |
| Purple sweet potato | Anthocyanin |
| Purple cabbage | Anthocyanin |
| Purple carrot | Anthocyanin |
| Purple Asparagus | Anthocyanin |
| Purple basil | Anthocyanin |
| Purple tomato | Anthocyanin |
| Purple cauliflower | Anthocyanin |
| Blackcurrants | Anthocyanin |
| Purple grapes | Anthocyanin |
| Purple figs | Anthocyanin |
| Elderberries | Anthocyanin |
| Purple guava | Anthocyanin |
| Purple mangosteen | Anthocyanin |
Many purple fruits and vegetables contain anthocyanins. These pigments act as antioxidants that protect the plants from stresses like sun exposure, cold temperatures, and insect damage. When anthocyanin concentration is especially high, it can create a vivid purple color.
The depth of purple varies based on anthocyanin content, pH, and other conditions. More acidic or neutral pH levels lead to bluer purples, while higher pH pushes the color toward vivid violet and magenta hues.
Purple Leaves
While less common than flowers and fruits, some plants also exhibit purple coloration in their stems and leaves. Examples include:
- Purple basil – Contains anthocyanins in its stems and leaf veins
- Purple shamrock – Leaves contain anthocyanins, especially when exposed to cooler temps or high light
- Purple cabbages and kales – Leaves become purple from anthocyanins
- Purple dead nettle – Leaves and stems are a violet color
- Purple heart – Deep purple leaves caused by betacyanins
- Purple fountain grass – Has a reddish-purple foliage
As with fruits and flowers, leaf anthocyanins serve a protective role. But in some plants like coleus, the pigments are simply for show. These decorative anthocyanins accumulate in the leaves regardless of environmental factors.
Purple Insects and Arachnids
In addition to plants, some insects and arachnids display naturally occurring purple and violet hues.
Beetles
Many beetles in the order Coleoptera exhibit metallic purple coloring. This includes:
- Violet ground beetles
- Purple emerald beetles
- Figeater beetles
- Grapevine beetles
- Margined blister beetles
Rather than pigments, these shiny, violet-colored beetles have physical structures on their exoskeleton that interfere with reflected light. This creates an iridescent effect that shifts from purple to green depending on viewing angle.
True Bugs
Some true bugs (order Hemiptera) also produce natural purple hues, like:
- Milkweed bugs
- Purple-shouldered late stink bugs
- Variable purple sharpshooters
- Violet seed bugs
In most cases, the purple color comes from pigments concentrated in the bugs’ wings and upper shell segments. This coloration serves as a warning signal to predators.
Butterflies and Moths
Many species of butterflies and moths exhibit purple wings, including:
| Insect | Pigment |
|---|---|
| Limenitis butterflies | Pterin pigments |
| Purple emperor butterflies | Pterin pigments |
| Atlides halesus moths | Ommochromes |
| Purple-winged grasshopper moths | Ommochromes |
Butterfly purple tones come from pterin pigments like xanthopterin and erythropterin. Moth purples contain ommochromes, which give many species red, yellow, and purple-brown hues.
Spiders
Some spiders also showcase brilliant purple colors, including:
- Argiope bruennichi orb-weavers
- Maratus volans peacock spiders
- Purple corrugated button spiders
In most spiders, these rich violet tones come from physical structures rather than pigments. Microscopic ridges, hair-like setae, and other anatomical features interfere with reflected light to generate vibrant purple as part of the spiders’ cryptic coloration.
Purple Minerals and Gems
In addition to flora and fauna, several naturally occurring geological formations also exhibit true purple shades.
Purple Minerals
There are a handful of purple mineral varieties found in nature, including:
| Mineral | Composition |
|---|---|
| Lepidolite | Lithium, aluminum, fluorine, hydroxyl |
| Lithiophilite | Manganese phosphate |
| Purpurite | Manganese phosphate |
| Purple fluorite | Calcium fluoride |
| Purple halite | Sodium chloride |
| Purple passionite | Potassium chromium sulfate |
These minerals get their violet color from trace elements like manganese that become incorporated into the crystal structures. The concentrations and oxidation states of these elements determine the final shade.
Purple Gemstones
Natural purple gems are quite rare, but a few do exist, such as:
- Amethyst – Purple variety of quartz
- Sugilite – Potassium sodium iron silicate
- Charoite – Hydrated calcium sodium potassium silicate
- Purple sapphire – Aluminum oxide
- Purple spinel – Magnesium aluminum oxide
Trace elements like iron and manganese are responsible for the color. These can get trapped in the crystal structures as the gems form, generating a range of violet, lilac, and purple tones.
Other Natural Purple Things
Beyond plants, animals, and geology, some other naturally occurring purple things include:
- Purple snails – Some sea snails in the family Muricidae have purple shells, such as Hexaplex trunculus.
- Purple frogs – The Indian purple frog secretes an indigo-colored mucus.
- Purple coral – Some coral like Melithaea ochracea are naturally deep purple.
- Purple lakes – Hypersaline lakes can turn purple from salt-loving microbes.
- Purple rocks – Wind