Mineralogy Glossary

Essential terms and definitions for mineralogy and mineral collecting.

Optical Properties

The billowing, floating light effect seen in moonstone (orthoclase/albite), caused by light scattering from thin …

The star-like optical phenomenon seen in certain cabochon-cut minerals, produced by light reflecting from oriented …

A glittery, sparkling optical effect caused by reflections from flat, oriented platelets of a contrasting …

The splitting of a light ray into two polarized rays when passing through an anisotropic …

The cat's-eye effect seen in certain cabochon-cut minerals, caused by parallel fibrous inclusions or hollow …

The separation of white light into spectral colors as it passes through a mineral, caused …

The emission of visible light by a mineral when exposed to ultraviolet radiation. Named after …

The iridescent play of color seen in labradorite feldspar, caused by interference of light from …

The quality and intensity of light reflected from a mineral's surface. Major types include metallic, …

A milky, iridescent light effect caused by the scattering of light from very fine particles …

The spectral iridescence displayed by precious opal, caused by the diffraction and interference of light …

The property of showing different colors when viewed along different crystallographic directions, caused by differential …

A measure of how much light slows down and bends when passing through a mineral, …

A metallic, bronzy iridescence caused by reflection from thin oriented exsolution lamellae or platelet inclusions …

The degree to which light passes through a mineral: transparent (clear), translucent (light passes but …