What is Diaphaneity?

Diaphaneity: How Much Light Can Pass Through

Diaphaneity is an optical property that describes how much light can pass through a material without being scattered or absorbed.

The word 'diaphaneity' originates from the Greek word 'diaphanēs', which means 'transparent' or 'to show through'. It combines the Greek roots 'dia', meaning 'through', and 'phaino', meaning 'to show' or 'to appear'.

Over time, 'diaphaneity' was adopted into the field of mineralogy and other scientific disciplines to describe the degree of transparency or translucency of minerals, gemstones, and other substances. In other words, how well a substance allows light to pass through.

A transparent material allows light to pass through with little or no scattering, allowing objects to be seen clearly. Glass is transparent.

A material that's translucent allows some light to pass through, but some is scattered or diffused. An object viewed through a translucent material can be seen but is blurred or obscured. An example is frosted glass.

Metal and wood are opaque, so they don't allow any light to pass through.

The diaphaneity of a substance depends on its crystal structure, as well as any impurities or inclusions.

Some translucent gemstones can initially appear to be opaque until they're held up towards the light.

The degree of translucency in a mineral or gemstone can vary considerably. Agate can be virtually opaque to highly translucent.

Transparent and highly translucent gemstones tend to be faceted. Opaque stones, or those that exhibit low translucence, are usually cut as cabochons.