Minerals often hold captivating secrets, revealing hidden properties under specific conditions. One such phenomenon is luminescence, where certain minerals absorb energy from light and then re-emit it, often in a stunning display of color. Among these, some stones possess a remarkable ability to transform their appearance, showcasing a vibrant glow when exposed to ultraviolet (UV) light, commonly known as black light.
The Stone That Shines Pink
The mineral specifically known for its distinct pink or reddish-pink glow under black light is Hackmanite. In its usual state, Hackmanite often appears in subtle hues such as white, gray, or a pale greenish color. However, when illuminated by UV light, it undergoes a striking change, developing vivid shades of pink, violet, or deep purple. Hackmanite is a variety of sodalite and is found in several locations globally, with notable deposits in Greenland, Quebec (Canada), Afghanistan, and Myanmar. The specimens from these regions can vary in the intensity and specific shade of their color change.
The Science Behind the Pink Glow
The pink glow observed in Hackmanite under UV light is due to a phenomenon called tenebrescence, also known as reversible photochromism. Unlike typical fluorescence, where a mineral emits light only while under UV exposure, tenebrescence involves a temporary color change that persists even after the UV source is removed. This process occurs because specific defects within the mineral’s crystal lattice, often referred to as color centers, are present. When UV light strikes Hackmanite, electrons within these defects absorb the energy and shift to new, higher-energy positions, becoming trapped. Trace elements, particularly sulfur, play a significant role in enabling this electron trapping and subsequent color change, as these trapped electrons gradually return to their original lower-energy states, causing the visible pink or purple coloration that slowly fades over time.
Observing and Identifying Hackmanite
To observe Hackmanite’s pink glow, using a long-wave UV light source is recommended, such as a 365nm UV flashlight. While short-wave UV light (254nm) can also induce the color change, long-wave UV is generally more accessible and effective for this purpose. When testing a specimen, expose it to the UV light and observe the rapid development of the pink or reddish-purple color. After removing the UV source, note how the color gradually diminishes, eventually returning to the stone’s original pale shade. This reversible fading helps distinguish Hackmanite from other fluorescent minerals that may glow different colors but do not exhibit this temporary color change.