What is Iridescence?
Iridescence Caused by Reflections
Iridescence is an optical phenomenon that causes colours on a surface to change depending on the angle from which they're viewed or illuminated.
It's caused by multiple reflections in multi-layered semi-transparent surfaces. Materials that can exhibit iridescence include soap bubbles, butterfly wings, peacock feathers and some crystals and minerals.
Clear quartz, mother of pearl, rainbow moonstone and labradorite all exhibit iridescence.
Iridescence in crystals is caused by the reflection and refraction of light.
Inclusions within a crystal or mineral interfere with light as it passes through. Inclusions are often made up of very fine layers. As light reflects off individual layers it produces a spectrum of colours.
Natural light is made up of red, orange, yellow, green, blue, indigo and violet. When these seven colours combine the human eye perceives them as white. Daylight is an example of what is correctly known as white light.
When white light passes through a prism the colours slow down and travel at different speeds. This is known as refraction.
Another optical phenomenon known as dispersion splits light into its component colours. That can be seen through a prism.
The reason we see a rainbow is because each raindrop acts as a tiny prism. The light refracted from the sun causes each droplet to send a spectrum of colours in many directions.
Iridescence can also be seen when a film of oil interacts with water. This can sometimes be seen when filling the car with petrol in the rain.
This type of iridescence occurs because light reflects off fine layers in the oil as it engages with the surface of the water. Each layer has a different thickness so as light passes through it produces a spectrum of colours.
The colours that can be seen depend on the thickness of each layer.
Iridescence is an optical phenomenon that occurs when light is either weakened or amplified as a result of passing through transparent or semi-transparent layers of varying thickness. It happens because the light is being scattered in different directions.
The word "iridescence" comes from the Greek word "iridos" meaning "rainbow". "Iridos" comes from the word "iris". In Greek mythology the Goddess Iris was the personification of the rainbow and a messenger of the gods.
The suffix "escence" which means "process or state of being" comes from the Latin "escent" meaning "having a tendency toward".
The optical phenomenon of iridescence is also known as "goniochromism". The prefix "gonio" comes from the Greek "gonia" meaning "angle" and "chroma" which means "colour".
Iridescence is seen when the surface of an object appears to change colour. It's dependant on the angle at which the object is being viewed and the angle of the light source.
It's caused by the reflection of light off multiple transparent or semi-transparent layers. The thickness of the layers can affect the iridescence in different ways.
Iridescence is a colourful shimmering effect that appears on certain surfaces due to the way they reflect light.
The butterflies in our photo are on display in the Harvard Museum of Natural History, Massachusetts, USA. Photo by Stone Mania.
The double rainbow is courtesy of Stan Celestian. Both images are clickable and redirect to the original photos.
The quartz crystal is from our collection. The final photo shows iridescence in a granite kitchen worktop.
