Of quartz – A colourful problem

Where does colour come from? Pigments, we say: the ability of certain materials to absorb and reflect different colours of light as electrons are excited along or within their structure. It’s true: sometimes we have to go as deep down as the chemistry, the connectivity between atoms, to see where colour comes from. Other times we don’t.

Structural colour arises from the nanostructure of materials: the arrangement of atoms in giant structures, or of groups of molecules. As they cluster together, they form planes, angles, surface details, and other interesting geometry with gaps and overlaps the same size as the wavelength of light. Like the colours seen on an oil slick, this structural colour happens when light interacts with the shape of matter.

What colour were the dinosaurs?

The discovery that some dinosaurs were feathered rather than the initially-assumed scaly took palaeontology by storm. But the question didn’t end there. We still don’t know the extent to which feathers were found across the dinosaur kingdom. Skin-impressions of some sauropods show hexagonal scales or bony plates, suggesting they were unfeathered, whilst others such as the tyrannosaurus were definitely feathered. And what colour were these scales or feathers? For the most part, we don’t know.

Feathered velociraptor. Matt Martyniuk via Wikipedia Commons