What is Schiller?

Schiller: A Descriptive Optical Term

Schiller is a broad descriptive term in mineralogy for the shimmering or reflective appearance seen in some rocks, minerals, and gemstones. It can be used for any stone that appears to shimmer, flash, or show colours when viewed from different angles.

Schiller is not the name of a specific optical phenomenon, which is why more precise terms are used for different materials.

Schiller in Relation to Labradorite

The flash of colour seen in labradorite (and rainbow moonstone, which is a trade name for white labradorite) is correctly known as labradorescence.

Labradorescence is the specific optical phenomenon responsible for labradorite’s flashes of colour. It's caused by light interacting with microscopic layered structures inside the crystal, producing the characteristic blue, green, gold, or multicoloured flashes.

While labradorite may be described as showing schiller in a general sense, labradorescence is the correct geological term for the effect in this mineral.

Specifically Named Optical Phenomena

Several optical phenomena exist in mineralogy to distinguish different visual effects:

Labradorescence
The colour flashes seen in labradorite

Adularescence
The soft, glowing light that appears to float on the surface of moonstone (orthoclase feldspar, not rainbow moonstone)

Aventurescence
The sparkling or glittery effect seen in aventurine and sunstone due to mineral inclusions

Schiller
A general descriptive term, while labradorescence, adularescence, and aventurescence are specific named optical phenomena.

Origin of the Term

The word schiller comes from German and is derived from schillern, meaning to shimmer or to gleam. Over time, it has been translated and interpreted in various ways, including twinkle, iridescence, and colour play.

As the science of mineral optics developed, the term remained in use as a broad visual descriptor rather than a strict scientific classification.

Article Photo

The labradorite stone in our photo is shown with and without labradorescence. The effect disappears when the direction of light changes. Photo: Courtesy of Stan Celestian.