What property does fluorescence describe?

Fluorescence is a property that specifically refers to the ability of a mineral to emit visible light when exposed to ultraviolet (UV) light or other forms of radiation. When a mineral contains certain impurities or specific structural characteristics, it can absorb the energy from UV light and then re-emit it as visible light, creating a glowing effect. This phenomenon is commonly observed in various minerals used in gemology and geology.

The other options describe different properties that do not relate to fluorescence. The ability to absorb radiation is a more general property and doesn’t specifically indicate the re-emission of light. Hardness is a measure of a mineral's resistance to scratching, which is unrelated to light emission. The chemical composition of a mineral outlines the elements it contains and their ratios but does not involve the behavior of light under UV exposure. Therefore, the correct choice clearly highlights the distinctive characteristic of fluorescence as it pertains to the glowing effect when a mineral is subjected to ultraviolet light.