Hackmanites

Hackmanites are a rare variety of the mineral sodalite, distinguished by their unique photochromic properties. This means that when exposed to ultraviolet (UV) light, hackmanites develop a distinct color, which then fades back to their original state over time in the absence of UV light. The intensity and duration of the color change depend on factors such as the specific chemical composition of the hackmanite and the duration and intensity of the UV exposure.

The most common color change observed in hackmanites is from a pale yellowish or colorless to a vibrant purple or pink hue. This phenomenon is thought to be caused by the presence of sulfur atoms within the mineral's crystal structure. When UV light strikes these sulfur atoms, it causes them to change their electronic state, resulting in the absorption and reflection of light in a way that produces the visible color. As the sulfur atoms revert to their original state, the color disappears.

Hackmanites are found in a few locations worldwide, with notable occurrences in Mount St. Hilaire in Quebec, Canada, and parts of Afghanistan. Due to their unusual color-changing ability, hackmanites are highly prized by mineral collectors and gem enthusiasts. They are typically faceted for use in jewelry, but their sensitivity to light means they should be stored away from direct sunlight to preserve their color. The scientific study of hackmanites contributes to our understanding of mineraluminescence and photochromic materials.