It is called the marble berry or more scientifically, Pollia condensata and it is found in Africa. These shiny berries are hard as a rock and more of a seed. Even though they are called a fruit they are inedible. The secret of the berry lies in how it achieves its brilliant color. It is something called structural color. Some animals such as peacocks, beetles and morpho butterflies use different materials and structures to get their iridescence but this is the first known plant.
Most colors are produced by pigments, or chemicals that selectively absorb and reflect different wavelengths of light. Paints are a blend of several pigments, intended to reflect light in such a way that you see a specific color.
“The cell walls in the skin of the berry contain small threads arranged like rows of matches. These threads form layers, each layer set off at a slight angle to the layer below, so that the rising layers forms a spiral pattern. The threads themselves are not colored blue. The color comes from the way the threads are loaded.Because of this, structure, no pigment, is the key to the Berry’s deep metallic shade and attractive color, Most cells appear blue. But from different angles, some radiate a green, pink, or yellow color because of subtle changes in the layers. Moreover, when looked closely, the colors are not smooth and even but appear pixelated, like the colors on a computer screen.” F.I.T.
What is really exciting about structural color is that unlike with pigments, the color does not fade over time. Berries found from long ago are just at brilliant.